High-Amylose Sodium Carboxymethyl Starch Matrices

Research ArticleHigh-Amylose Sodium Carboxymethyl Starch MatricesDevelopment and Characterization of Tramadol HydrochlorideSustained-Release Tablets for Oral Administration

Teresa Nabais and Greacutegoire Leclair

Faculte de Pharmacie Universite de Montreal PO Box 6128 Downtown Station Montreal QC Canada H3C 3J7

Correspondence should be addressed to Gregoire Leclair gregoireleclairumontrealca

Received 22 January 2014 Accepted 2 March 2014 Published 8 April 2014

Academic Editors T M Belle Bresolin K Goracinova and R Zelko

Copyright copy 2014 T Nabais and G Leclair This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Substituted amylose (SA) polymers were produced from high-amylose corn starch by etherification of its hydroxyl groups withchloroacetate Amorphous high-amylose sodium carboxymethyl starch (HASCA) the resulting SA polymer was spray-driedto obtain an excipient (SD HASCA) with optimal binding and sustained-release (SR) properties Tablets containing differentpercentages of SDHASCA and tramadol hydrochloride were produced by direct compression and evaluated for dissolution Once-daily and twice-daily SDHASCA tablets containing two common dosages of tramadol hydrochloride (100mg and 200mg) a freelywater-soluble drug were successfully developed These SR formulations presented high crushing forces which facilitate furthertablet processing and handling When exposed to both a pH gradient simulating the pH variations through the gastrointestinaltract and a 40 ethanolmedium a very rigid gel formed progressively at the surface of the tablets providing controlled drug-releasepropertiesThese properties indicated that SDHASCAwas a promising and robust excipient for oral sustained drug-release whichmay possibly minimize the likelihood of dose dumping and consequent adverse effects even in the case of coadministration withalcohol

1 Introduction

Starch is a naturally occurring and a biodegradable polymerthat is metabolized by the human body Besides beingnontoxic starch is an abundant cost-effective and renewablematerial [1] Due to these advantages starches and modifiedstarches have beenwidely and safely used in the food industryas thickeners enhancers of organoleptic properties or tex-ture modifiers and in the pharmaceutical industry as fillersbinders disintegrants [2] and more recently as hydrophilicexcipients for controlled drug-release Numerous starch-modification methods such as chemical [3] physical (iegelatinization) [4] enzymatic [5] or a combination thereofhave been employed to produce new starch products withspecific properties Starch is a good candidate for chemicalreaction or transformation because it is composed of amyloseand amylopectin two glucose polymers presenting threehydroxyl groups accessible as chemically active functionalentities Some of the modifications commonly employed to

prepare starch derivatives are carboxymethylation ethoxyla-tion and oxidation [6]

Substituted amylose (SA) has been introduced as apromising pharmaceutical excipient for sustained drug-release SA matrix tablets have been prepared by directcompression which is the easiest way to manufacture an oraldosage form and consists of dry mixing of drug and SA poly-mers followed by compression [7 8] The first SA polymershowing good properties as an excipient for sustained-release(SR) was produced by an etherification process using high-amylose corn starch and glycidol as the substituent and wasreferred to as SAG-27 where G defines glycidol and 27represents the degree of substitution (DS) expressed as theratio of mole of substituent per kilogram of amylose [7 8]These properties included almost constant in vitro drug-release [7ndash9] no significant influence of compression forces(CF) ranging from 05 to 50 tonscm2 on the drug-releaseproperties [9 10] large ranges of use for drug loading drug

Hindawi Publishing CorporationISRN PharmaceuticsVolume 2014 Article ID 391523 13 pageshttpdxdoiorg1011552014391523

2 ISRN Pharmaceutics

solubility and tablet weight (TW) [7 11] and unusually highcrushing force values [10]

The use of sodium chloroacetate or chloroacetic acidin place of nonionic substituents like glycidol has beensubsequently proposed to produce an excipient more readilyacceptable by regulatory agencies for its nontoxicity [8 12]Sodium carboxymethyl starch with low-amylose content wasalready awell-knowndisintegrant agent in immediate-release(IR) tablets [13] High-amylose sodium carboxymethyl starch(HASCA where ldquoHASrdquo means high-amylose substitutedstarch and ldquoCArdquo defines the substituent used herein chloroac-etate) contrariwise has been introduced as a promisingpharmaceutical excipient for oral SR tablets prepared bydirect compression [12] Contramid a cross-linked highamylose starch has already been used in tablets as a retardingagent [14]

After being initially produced on laboratory scale thepolymer was obtained on an industrial pilot scale Howeverthese latter batches of polymer were unsuitable for tabletingand sustained drug-release due to inadequate physical prop-erties For this reason the material was spray-dried (SD) toobtain a compressible excipient This procedure which hasbeen described elsewhere [6] resulted in SD HASCA thepolymer used in the current study

Studies on the in vitro release characteristics ofacetaminophen from tablets composed of SD HASCAdrug and sodium chloride have demonstrated the suitabilityof this polymer as a sustained drug-release excipient Noburst effect was observed even in the presence of largeamounts of soluble sodium chloride in the formulation[15 16] Moreover the release of acetaminophen fromoptimized SD HASCA formulations is not significantlyinfluenced by the variations of pH and residence time inacidic media [16] These prior results suggest that drug-release from SDHASCA tablets may not be affected by intra-and intersubject variations in gastric pH or gastric residencetime Acetaminophen (phenol pKa 951) and tramadolhydrochloride (tertiary amine pKa 941) are completelynonionized and completely ionized at physiological pHrespectively Moreover a first in vivo study where the sameoptimized SD HASCA formulation was administered orallyto healthy human subjects has demonstrated extendedacetaminophen plasma levels and demonstrated that the gelformed by the polymer was strong enough to resist boththe powerful peristaltic contractions normally occurringin the fasted state and biodegradation in the intestine [16]Other features of SD HASCA that confirm the potential ofthis polymer for sustained drug-release include its excellentbinding properties in the absence of binders which resultedin very high crushing forces [6 15] A strong dependence ofdrug-release on TW has also been found corresponding to aTW rise to an increased total release time [15]

Tramadol is a synthetic centrally acting analgesic agentwith a dual mechanism of action [17] It has proven to beeffective in the treatment of moderate to moderately severepain without causing severe side effects and organ damages[18] For the treatment of chronic pain frequent oral admin-istration of IR tramadol is required (at least four times daily)because of its mean elimination half-life which can vary

from 5 to 7 h in humans [19] In adults and adolescents theusual oral dosage regimen is 50 to 100mg every 4 to 6 hourswith a maximum dosage of 400mgday [17] Consequentlyoral formulations of tramadol that provide a more gradualrelease of the drug have been developed with the aim ofreducing the frequency of administration minimizing acuteadverse effects and thus improving the patient compliance[20 21] After oral administration tramadol is rapidly andalmost completely absorbed Its bioavailability of 70 after asingle administration can be attributed entirely to extensivefirst pass metabolism [22] However at steady state thebioavailability of a SR formulation has been shown to be 100relative to an IR formulation [23] which represents anotheradvantage of SR formulations of tramadol Bioequivalenceafter dose adjustment between IR and SR formulations hasbeen demonstrated [19] Tramadol hydrochloride is readilysoluble in water and ethanol and hence judicious selectionof release retarding excipients is necessary to achieve anextended in vivo input rate of the drug

SR formulations especially those designed for once-daily administration contain amounts of drug that can bepotentially risky if released as a burst commonly called dosedumping Tramadol hydrochloride may cause severe sideeffects if high plasma concentrations are reached quicklyInadvertent or intentional misuse of a SR formulation withconsequent dose dumping may include breaking crush-ing tablets and simultaneous coingestion of the medica-tion with high doses of ethanol Therefore the robustnessof SD HASCA tablets in an ethanolic medium and theircrushing strength values are important factors to take intoaccount

In this study the in vitro release characteristics frommatrix tablets comprising tramadol hydrochloride as themodel drug and SD HASCA as the only SR excipient wereevaluated in a series of buffers simulating the pH of thefluids throughout the gastrointestinal tract Tablets intendedto twice-daily and once-daily administration were devel-oped These tablets contained 100 mg and 200 mg of drugrespectively The dissolution profiles of these tablets werecomparedwith those ofmarketed tramadol hydrochloride SRformulations of the same drug content The resistance of thegel formed by SD HASCA to an alcoholic medium was alsoinvestigated

2 Materials and Methods

21 Materials Amorphous HASCA (Eurylon 6 batch 3910ref 799511) was provided by Roquette Freres (LestremFrance) and contained approximately 60 of amylose and40 of amylopectin The DS was equal to 0045 (numberof moles of substituentnumber of moles of anhydroglucose)[15] Tramadol hydrochloride was purchased from JubilantOrganosys Ltd (Nanjangud Mysore India) Commerciallyavailable tramadol tablets Tridural 100mg and 200mgRalivia 200mg Zytram XL 200mg Topalgic LP 100mg and200mg and Contramal LP 200mg were purchased frompharmacies in Canada and in France All chemicals were ofreagent grade and were used without further purification

ISRN Pharmaceutics 3

Table 1 SD HASCA tablets formulation press used target CF and thickness and selected twice-daily and once-daily tablets

TW (mg) of drug (ww) Tablet press Target CF(tonscm2) HP

Target thickness(mm) SSP

Selected twice-dailyand once-daily tablets

400

125 HP 25 mdash mdash25 HP 25 mdash mdash375 HP 25 mdash mdash50 HP 25 mdash mdash60 HP 25 mdash mdash

450 2222 HP 25 mdash Twice-daily (not selected)

500

20 HP 25 mdash mdash30 HP 25 mdash mdash40 HP 25 mdash Twice-daily (not selected)50 HP 25 mdash mdash60 HP 25 mdash mdash

700

143 HP 1 mdash mdash143 HP 15 mdash mdash143 HP 2 mdash mdash143 HP 25 mdash Once-daily (not selected)

800

125 HP 25 mdash mdash25 HP 25 mdash Once-daily (not selected)375 HP 25 mdash mdash50 HP 25 mdash mdash60 HP 25 mdash mdash

450 2222 (100mg) SSP mdash 463 Twice-daily (selected)500 40 (200mg) SSP mdash 515 Twice-daily (selected)700 143 (100mg) SSP mdash 698 Once-daily (selected)800 25 (200mg) SSP mdash 743 Once-daily (selected)

22 Preparation of HASCA Tablets Amorphous HASCA asprovided by its manufacturer did not possess the requiredbinding and SR properties to be used as a suitable materialfor SR tablets prepared by direct compressionTherefore thispolymer was spray-dried as described by Brouillet et al [6]by first preparing a suspension of HASCA in a mixture ofwater and ethanol (final waterethanol ratio of 133 4mL ofethanolg of HASCA) and then spray-drying using a BuchiB-290 Mini-Spray-Dryer (Flawill Switzerland)

Tablets were prepared by direct compression using a 30-ton manual hydraulic press (referred to herein as HP C-30Research amp Industrial Instruments Company London UK)equipped with round flat-faced tooling (diameter 126mm)or a single-stroke press machine (referred herein as SSPManesty F3 Machine Manesty Machines Ltd LiverpoolUK) also equipped with round flat-faced tooling (diameter111mm) In the HP compression force was adjusted to targeta specific CF and in the SSP compression force was adjustedto target specific thickness SD HASCA tablets of differenttotal weights containing different percentages of polymer anddrug were produced as described in Table 1

23 Tablets Characterization and In Vitro Drug-Release Eval-uation The crushing forces (Newton) of SD HASCA tabletswere measured using a hardness tester (Pharma Test Type

PTB 301 Hainburg Germany) and their thickness using anelectronic caliper (Starrett 799A Series)

The in vitro drug-release properties of SD HASCA SRtablets in simulated gastric fluid (stage I) and simulatedintestinal fluids (stage II and stage III) were assessed usinga USP apparatus 2 (900mL 37∘C 50 rpm) [24]

During stage I the tablets were exposed to hydrochloricacid buffer (pH 12) simulating gastric pH (SGF) for 1 hDuring stage II the tablets were exposed to phosphate buffer(pH 68) simulating jejunum pH (SIF I) for an additional 3 hFinally the tablets were exposed to a second phosphate buffer(pH 74) simulating ileum pH (SIF II) until the end of theassay (total time of 24 h) All standard buffer solutions wereprepared according to the USP

In addition dissolutions tests in a 40 ethanol in watersolution were performed to assess the release properties of aSD HASCA formulation and a commercial formulation withthe same drug content and the same frequency of admin-istration This percentage of ethanol was chosen because itrepresents a standard strength of alcoholic spirits [25] Testsin alcohol were carried out during 7 h

To avoid eventual floating to the surface of the mediumor adhesion to the vessel each tablet was placed inside aperforated cylindrical plastic cage (Figure 1) The cage hadenough internal space for drug-release to occur from all


Figure 1 Plastic cage used in the dissolution experiments to avoideventual adhesion to the vessel or floating

sides of the matrix and its perforations were big enough notto interfere with the circulation of the medium inside thedissolution vessel but on the other hand were small enoughto keep the tablets inside

According to USP specifications the paddle should bepositioned at a distance of 25 mm of the inside bottom of thevessel Due to the presence of the cage at the bottom of thedissolution vessel the paddle was positioned at a distance of75mmof the inside bottomof the vessel After each samplingan equivalent volume of fresh medium (10mL) was addedEach experiment was performed in triplicateThe occurrenceof macroscopic transformations in the matrix tablets andtheir eventual influence on the release profiles were regis-tered Samples were filtered through syringe filters (045mmnylon) Tramadol hydrochloride release was followed by UVspectrometry (271 nm) A calibration curve was prepared foreach of the three mediums (pH 12 68 and 74) as well as forthe ethanolic medium and anew before the measurement ofthe samples resulting from each dissolution test The drug-release results are expressed as cumulative percentage () asa function of time (h)

The in vitro release properties of twice-daily and once-daily commercial formulations with 100mg or 200mg oftramadol hydrochloride were also evaluated using the sameexperimental conditions so as to provide a direction regard-ing the desired release times The twice-daily dosage formstested were Topalgic LP 100mg Topalgic LP 200mg andContramal LP 200mg and the once-daily dosage formstestedwere Tridural 100mg Tridural 200mg Ralivia 200mgand Zytram XL 200mg

24 Modifications to the United States Pharmacopoeia (USP)Method In the first in vitro studies on the release of tra-madol hydrochloride from SD HASCA matrix tablets someformulations showed a propensity to float or to adhere tothe bottom of the vessel This propensity was higher asthe concentration of tramadol hydrochloride increased Thissituationmakes the tablets very susceptible to large variationsin hydrodynamic conditions that prevail in a dissolutionvessel In addition the tablets floating at the surface of thedissolution medium or adhering to the glass surface had alower surface area in contact with the mediumThis situation

can affect drug-release from the tablets as the exposedsurface area is a major factor determining release kineticsboth in erosion-controlled as well as diffusion-controlledsystems [26]

The use of perforated cylindrical plastic cages placedbelow the paddles in the dissolution vessels appeared to besuccessful in preventing adhesion to the vessel and floatingThis solution was chosen in detriment of the use of USPapparatus I (basket) as the use of this apparatus can interferewith the free swelling of the matrix However the paddlerelative position had to be at a higher height comparedto what is settled by the USP because of the size of thecage Hence the influence of the paddle position on drug-release was evaluated using acetaminophen 700-mg tabletsThese tablets were composed of acetaminophen (40) andHPMC (60) Equivalent dissolution (119891

2= 9977) was

achieved when the paddle was positioned according to USPspecifications (25mm) and when the paddle was positionedhigher (75mm)

25 Statistical Analysis and Formulations Comparison Thearithmetic average and the standard deviation of the cumula-tive of drug released at predetermined time intervals werecalculated

Dissolution profiles were compared using the similarityfactor (119891

2) according to the following equation proposed by

Moore and Flanner [27]

1198912= 50 times log[1 + (1

119899)119899

sum119905minus1

(119877119905minus 119879119905)2

]

minus05

times 100 (1)

where 119877119895and 119879

119895are the percent dissolved of the reference

and test products at each time point 119895 and 119899 is the numberof pool points Two dissolution profiles are similar if 119891

2

is between 50 and 100 according to the Food and DrugAdministration (FDA) and the European Agency for theEvaluation ofMedical Products (EMEA) However the closerto 100 ()119891

2 themore similar the dissolution profiles areThe

dissolution profiles were also compared using the values ofthe time to release 50 (T50) and to release 90 of drug(T90)

3 Results and Discussion

31 Measurement of Tablet Crushing Strengths in Order toGuarantee the Reproducibility of the Spray-Drying MethodThe reproducibility of the method used to transform amor-phous HASCA into SD HASCA was assessed through theevaluation of tablet crushing forces for different batches SDHASCA tablets weighting 200mg were prepared by directcompression The excipient was compressed at a CF of25 tonscm2 using a HP using a dwell time of 20 secondsThe values of the crushing forces of 200-mg tablets producedfrom different batches of SD HASCA varied between 1249 plusmn105 and 1485 plusmn 32Newton (arithmetic averages plusmn standarddeviations) Therefore the crushing forces were consideredreproducible As non-SD HASCA particles did not possessany biding properties and the SD procedure resulted in a


Table 2 Time to release 50 (T50) and 90 (T90) of drug from SD HASCA tablets with total weights between 400mg and 800mg and of drug (ww) between 125 and 60

TW (mg) [T50 T90] (h) of drug (ww)125 143 20 2222 25 30 375 40 50 60

400 T50 18 mdash mdash mdash 15 mdash 14 mdash 13 11T90 65 mdash mdash mdash 53 mdash 45 mdash 46 35

450 T50 mdash mdash mdash 19 mdash mdash mdash mdash mdash mdashT90 mdash mdash mdash 64 mdash mdash mdash mdash mdash mdash

500 T50 mdash mdash 255 mdash mdash 205 mdash 19 175 14T90 mdash mdash 875 mdash mdash 76 mdash 67 59 465

700 T50 mdash 4 mdash mdash mdash mdash mdash mdash mdash mdashT90 mdash 144 mdash mdash mdash mdash mdash mdash mdash mdash


decrease in particle size of the polymer it has been hypoth-esized that these unusual high crushing strength values aredue in part to the particle size reduction which correspondsto a higher surface area of the particulate product andprovides a higher number of binding points In addition it isbelieved that the combination of water and ethanol in the SDprocess has a plasticizer effect causing partial melting of thepolymer and particle rearrangement under compression [6]

32 Formulation Screening and Development of Twice-Dailyand Once-Daily SD HASCA Formulations with 100mg and200mg of Tramadol Hydrochloride The values of the T50andT90of tramadol hydrochloride from tablets of differenttotal weights and containing different percentages of polymerand tramadol hydrochloride (compressed with the HP) aresummarized in Table 2 Increasing the percentage of tramadolhydrochloride in the tablet led to an increase in the drug-release rate for all TWs which is a common observationfor hydrophilic matrices In addition the total release timeincreased significantly as a function of TW The T50 wasthough less affected by TW than the T90

When immersed in the dissolution mediums a veryrigid gel layer with high mechanical strength in the swollenstate formed on the surface of the tablets This strong gellayer which is formed by hydrogen bonding between thehydroxyl groups of the soluble gelled starch chains hasbeen documented before for SD HASCA [15] In additionits formation has been related to the pH-independent SRbehaviour of high-amylose sodium carboxymethyl starchproduced at low DS as it is the case of SD HASCA [28]The gel layer formed by SD HASCA showed a lower degreeof swelling when compared to the gel layer formed byhydroxypropylmethylcellulose (HPMC) (results not shown)The most important aspect of the release mechanism fromtablets constituted by hydrophilic polymers is known to bethe formation of a gel layer around the dry core of the matrixin response to water penetration This gel layer hinders fastinward medium penetration and outward drug diffusionPhenomena that govern gel layer formation and thereforedrug-release are penetration of the dissolution medium into

the matrix resulting in polymer hydration and swelling(relaxation process) drug dissolution and diffusion throughthe layer of swollen polymer and erosion on the surfaceof the matrix The formation of the gel layer is caused bythe polymer-state transition The gel layer acts like a barrieragainst the fast release of drugs whilst controlling at the sametime the penetration of aqueous medium and the diffusion ofdrug As the size of the internal dry andor partially hydratedcore of the tablets increases as a function of TW for thesame concentration of drug if the core is considered a drugreservoir the larger is the internal reservoir the longer is thetime to empty it which explains the increase of the totalrelease time as a function of TW Besides as demonstratedin a previous study augmenting TW heightens the contri-bution of diffusion to the detriment of erosion as the mainmechanism controlling drug-release leading to a decline inthe drug-release rate [15] Furthermore a combination oftwo release mechanisms has been described as controllingthe kinetics of drug-release from SD HASCA matrices drugdiffusion through the gel layer after drug dissolution (Fickiandiffusion) and polymer disentanglement and erosion (case IIrelaxational release) [15] Fickian diffusion release occurs bydiffusion of drug molecules due to a concentration gradientCase II relaxational release is the mechanism associated withpolymer-state transition from the glassy a solid state (drypolymer) to the rubbery state an expanded and flexiblestate which is linked with the polymer swelling process[29] Similar conclusions were reported for the transport ofacetaminophen fromnonionic SAmatrices [9 11] It is knownthat drug concentration and thickness of the gel layer arethe factors governing drug-release [30] At lower drug con-centrations that is higher polymer concentrations diffusionis the main transport mechanism and thus the total releasetime was longer However as drug concentration increasesthe drug-release rates also increase Tramadol hydrochlorideis freely soluble in water and thus dissolves quickly inaqueous medium Its high solubility along with an increasein drug loading resulted in higher drug concentration inthe gel In addition the high hydrophilicity of tramadolhydrochloride promotes the penetration of the dissolution


medium into the matrices Above a certain drug-loadingthreshold the quantity of absorbedwatermay be such that thewater-polymer interactions become superior to the polymer-polymer interactions causing chain disentanglement andpolymer dissolution [31] As a result progressive erosionappears on the surface of the tablets leading to a decreasein the thickness of the gel layer and an increase in the drug-release rate Indeed it has been reported that the gel strengthis an essential factor in the matrix performance and is con-trolled not only by the viscosity and chemical structure of therubbery polymer but also by its concentration [30]Thereforelower SD HASCA concentrations in the tablet led to lowergel strengths and thus to higher release rates owing tohigher erosion Besides it can be hypothesized that at certaindrugpolymer ratio the release process will become governedmainly by erosion However opposite results have beenobserved for tablets containing SD HASCA acetaminophenand sodium chloride In this case an increase in drug loadingcorresponded to an increase in total release time until acertain level where erosion occurred [15] It is importantto take into consideration the higher solubility of tramadolhydrochloride compared to acetaminophen Indeed whenformulating SDHASCAmatrices not only the concentrationof the components has to be taken into account but also theirsolubility nature and interactions between them

As the values of the time to release 25of drug (T25) fordifferent TWs were similar especially for the 400-mg tabletsthese values are not presentedTheT25 corresponds usuallyto the burst effect and depends on the amount of drug on thetable surface available for immediate dissolution and releasein the medium

The formulation screening allowed the investigation ofthe most adequate total weights for four formulations withSD HASCA as the SR excipient two twice-daily with 100mgand 200mg of tramadol hydrochloride and two once-dailywith 100mg and 200mg of tramadol hydrochloride In orderto select these formulations the in vitro drug-release profilesfrom tablets with 100mg and 200mg of drug which wereproduced using the HP to study the influence of drug contentandTWon the dissolution rate for the formulation screeningdescribed above were compared to the in vitro drug-releaseprofiles of commercially available twice-daily and once-dailytramadol hydrochloride formulations with the same drugcontentThe release profile from the tabletswith a total weightof 700mg containing 100mg of drug and compressed withthe HP at 25 tonscm2 for 20 seconds which were preparedto study the influence of the CF on the release rate was alsocompared to the release profile of commercial formulationsFigure 2 shows the drug-release profiles from the commercialonce-daily dosage forms

The values of T50 and T90 for the tablets weighting500mg with 200mg of tramadol hydrochloride were 19 and67 hours (Table 5) very similar to the values for Topalgic LP200mg 2 and 69 hours respectively (Table 3) In additionthe1198912resultant from the comparison of their profiles resulted

in value of 8654 Consequently the 500-mg tablet with 200 ofdrug was chosen as the twice-daily formulation with 200mgof drug

0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750

Tridural 100mgTridural 200mgRalivia 200mgZytram XL 200mg gt24

Figure 2 Cumulative of tramadol hydrochloride released in vitrofrom once-daily commercial formulations (◼ Tridural 100mg 998771Tridural 200mgX Ralivia 200mg and e Zytram XL 200mg)

An evaluation of the release characteristics of a for-mulation corresponding to a total weight of 450mg with100 of drug was also performed to determine if its releasecharacteristics approached better the ones of the 500-mgtablet with 200mgThe T50 and T90 for this formulationwere 19 and 64 hours (Table 5) very similar to valuesof the selected twice-daily SD HASCA formulation with200mg and more similar than the T50 and T90 forthe 400-mg and 500-mg tablets with 100mg of drug Inaddition the 119891

2results also showed that the 450-mg tablet

with 100mg of drug presented release characteristics moresimilar to the selected twice-daily formulation with 200mgof tramadol hydrochloride (119891

2equal to 8923) and to Topalgic

LP 100mg (1198912equal to 7271) which led to the selection of the

formulation weighting 450mg as the twice-daily SD HASCAformulation with 100mg Close similarity between both thetwice-daily and the once-daily developed formulations withdifferent contents of drug was desired

Given that SD HASCA formulations were produced fororal administration the size of the tablets had to be takeninto consideration when producing once-daily formulationsConsequently an increase in tablet size was not consideredand the tablet weighting 800mg with 200mg of drug waschosen as the once-daily formulation with 200mg of tra-madol hydrochloride even considering that the release ratefrom this tablet was faster than the rate from Tridural 200mg(1198912equal to 5583) In addition even though the release

from the tablets weighting 800mg with 100mg of tramadolhydrochloride was slower and more similar to Tridural100mg (119891

2equal to 681) than the tablet weighting 700mg

with the same drug content (1198912equal to 5309) the latter had a

profilemore similar to the tablet with a total weight of 800mgand 200mg of tramadol hydrochloride (119891

2equal to 8239)

the selected once-daily SD HASCA formulation with 200mgof drug Therefore the 700-mg tablet with 100mg of drugwas chosen as the optimal once-daily formulation with 100of tramadol hydrochloride

A pH gradient was used instead of a unique buffer ordistilled water because it provides amore accurate simulation


Table 3 Time to release 50 and 90 of tramadol hydrochloride [T50 T90] from twice-daily (every 12 hours) and once-daily (every 24hours) commercially SR formulations and SDHASCA formulations (produced with the SSP) with 100mg and 200mg of drug Release timesare presented in hours

(a) Frequency of administration twice-daily

FormulationCommercial SD HASCA (SSP)

Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]

(b) Frequency of administration Once-daily


Tridural 100mg Tridural 200mg Ralivia 200mg Zytram XL 200mg 100mg of drug (SSP) 200mg of drug (SSP)[610 1570] [600 1950] [640 1160] [750 gt24] [510 2040] [520 1910]

Table 4 Time to release 50 and 90 of tramadol hydrochloride[T50 T90] for SD HASCA tablets compressed between 1 and25 tonscm2 and similarity factors (119891

2) between tablets weighting

700-mg tablets with 100mg of tramadol hydrochloride compressedwith a 30-tons manual HP at different CFs

CF (tonscm2) [T50 T90] (hours) 1198912versus 25 tonscm2

1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]

of the environment that an oral dosage form encounters whentransiting through the gastrointestinal tract Besides studieshave shown that in vivo-in vitro correlations (IVIVC) areimproved when the dissolution tests are carried out in a pHgradient rather than in distilled water [32]

Studies have demonstrated that the DS has a significantinfluence on the structural physicochemical and drug-release properties of high-amylose carboxymethyl starch [2833] These studies have suggested that high-amylose sodiumcarboxymethyl starches produced at lower DS are preferablysuitable for use as an excipient for SR formulations showingextended-release in both acidic and alkaline dissolutionmedia while high-amylose sodium carboxymethyl starchat higher DS (referred to as CM-HAS) can be used asan excipient for delayed-release since the drug-release ratein acidic medium is significantly lower than in alkalinemedium [28 33] As a result the potential of this polymerproduced at higher DS as an excipient for formulations withgastroresistant properties of a variety of drugs includingbioactive agents has been investigated [34 35] The polymerused in this study was produced at a lower DS and thereforeshows SR properties in both acid and alkaline environment

33 Decrease of the Tablet Surface Area in Order to Increasethe In Vitro Release Time of Tramadol Hydrochloride fromOnce-Daily and Twice-Daily SD HASCA Matrix Tablets The

comparison between the T50 and T90 from the once-daily SDHASCA formulations with 100mg (4 and 144 h) and200mg of tramadol hydrochloride (41 and 164 h) preparedusing a HP (Table 5) and the T50 and T90 from Tridural100mg (61 and 157 h) and Tridural 200mg (6 and 195 h)the once-daily commercial dosage forms (Table 3) show thatthe release rates from the once-daily SD HASCA tablets wereslightly higher than the release rates from the commercialtablets Closer values were however found for the tabletsintended for twice-daily administration

The ultimate purpose of the developed SD HASCA SRformulations is oral administration in humans Tablet sizeshape and geometry are important factors to take intoconsiderationwhen designingmedication to be administeredby this route since they determine the level of patient comfortduring oral administration and thus compliance Besidesit has been shown that tablet size shape and surface areamay affect drug-release profiles [36 37] and can thereforebe used for modulation of drug-release rate A study on theinfluence of tablet surface areavolume (SAV) ratio on drug-release from controlled-release matrix tablets containingHPMC indicated a direct relationship between SAV ratiosand drug-release rate Utility of SAV to influence drug-release was demonstrated by altering tablet shape to adjustSAV [36] The importance of this finding is related to thepossibility of achieving optimal drug-release profiles withoutfurther modification of a formulation by simply choosing anappropriate SAV ratio for a tablet

Based on the higher comfort for the patient whenswallowing tablets with narrower diameters and the directlink found between surface area and drug-release rate thedimensions of the selected SR SD HASCA formulationswere changed so as to decrease their diameter decreasingthe tablet SAV ratio To achieve these changes the tabletswere compressed using a SSP machine instead of the 30-ton manual HP This compressing machine produced tabletswith an average diameter of 111mm instead of 126mm andconsequently tablet heights were thicker

When using the SSP the lower plunger nuts were adjustedso as to achieve a target average thickness of 7mm for the


Table 5 Time to release 50 and 90 (hours) of tramadol hydrochloride [T50 T90] from twice-daily and once-daily SDHASCA tabletswith 100mg and 200mg of drug compressed using a 30-tons manual hydraulic press at 25 tonscm2 (HP) or a single-stroke press (SSP)

Frequency of administration Formulation100mg of drug (HP) 100mg of drug (SSP) 200mg of drug (HP) 200mg of drug (SSP)

Twice-daily [190 640] [300 1070] [190 670] [300 1025]Once-daily [400 1440] [520 2040] [410 1640] [520 1910]

once-daily tablet with 100mg of drug(instead of 44mm ofthe tablets produced with the HP) 74mm for the once-daily with 200mg of drug (instead of 48mm of the tabletsproducedwith theHP) and 46mm for the twice-daily tabletswith 100mg and 52mm for the twice-daily tablets with200mg (no thickness measurements had been made with theHP) As the number of sample tablets was small it was notpossible to present the values of the standard deviations ofthe tablet thickness

The in vitro drug-release characteristics from the tabletsproduced with the SSP were then evaluated under the samepH gradient dissolution conditions Even though the twice-daily SD HASCA formulations presented a release profileclose to the profile of the commercial ones the same changesin surface area were studied so as to develop all the fourformulations under the same conditions and make them allmore easily swallowable

331 Preliminary Crushing Strengths Measurements Thecrushing strengths of 700-mg and 800-mg tablets with 100mgand 200mg of tramadol hydrochloride respectively com-pressed with the HP were measuredThe designed procedurewas to apply a CF starting at 1 tonscm2 and to increase itgradually up to 25 tonscm2 The tensile strength of thesetablets was so high that none of them broke after beingsubmitted to the hardness tester The hardness tester alloweda maximum measurable crushing force of 300N Thereforeno further measurements were necessary The very highcrushing strengths found for these tablets support the theorydescribed above of the occurrence of particle rearrangementandpartialmelting of the polymer under compression result-ing in the densification of the matrices The high crushingstrength values are an advantage when considering indus-trial manufacture because they ensure batch reproducibilitythroughout the process

332 Influence of CF on Tramadol Hydrochloride Release fromSD HASCA Tablets The influence of CFs ranging between1 and 25 tonscm2 on the drug-release properties from SDHASCAmatrix tablets weighting 700-mg tablets with 100mgof tramadol hydrochloride and compressed using a 30-tonsmanual HP was also investigated This range of CFs wasselected because it covers the normal range of CF employedat the industrial level The T50 and T90 for the testedCFs and the values of the 119891

2between tablets compressed

at different CFs are represented in Table 4 Between 1and 25 tonscm2 CF did not significantly influence drug-release from SD HASCA matrix tablets Similarly the drug-release was not significantly influenced by the compression

force for tablets containing 325 of SD HASCA 40 ofacetaminophen and 275 of sodium chloride compressed ata total weight of 400 and 600mg

These consistent results show that the independencebetween drug-release from SD HASCA matrices and the CFused is not affected by the different composition of the poly-mer the final ethanolHASCA ratio and the substitution ofsodiumchloride for tramadol hydrochloride as the electrolytein the formulation Ungur et al [12] have already noted thatin the case of lab-scale HASCA CF influencedmicroporositybut did not alter the drug-release rate A study using formula-tions composed of SD HASCA acetaminophen and sodiumchloride where the relationship between TW and CF versustablet thickness (TT)was investigated to understand the goodbiding properties of SD HASCA suggested that an intensedensification of the matrices occurred and was the samefor CFs ranging from 1 to 25 tonscm2 In this case it wasalso demonstrated that CF does not considerably influenceTT [15] This peculiar mechanism of densification that issintering by viscous flow and melting under compressionhas been demonstrated by scanning electron microscopy(SEM) and porosimetry for matrices composed of SAG-27[10] Such very low porosity might explain why CF does notinfluence the drug-release rate from tablets with SD HASCAor SAG-27 as the SR excipient As opposed to SAG-27 noinfluence of CFs on the amplitude of the burst effect as well ason the time-lag has also been observed for SDHASCA tablets

The fact that theCF applied did not significantly influencedrug-release is important since it indicates that the unknownCF exerted by the SSP machine may not have a significantinfluence on the release of tramadol hydrochloride from SDHASCA tablets compressed with this machine This findingand the very high crushing strengths further illustrate theutility of SD HASCA as a directly compressible excipient fororal sustained drug-release and assure the reliableness of theSSP

333 In Vitro Release of Tramadol Hydrochloride from Opti-mal Twice-Daily and Once-Daily SD HASCA Matrix TabletsAs shown in Figure 3 the 700-mg SD HASCA tablets(once-daily) with 100mg of drug compressed with the SSPmachine had a slightly lower release than the once-dailycommercial formulations after 10 hours of release At thisstage of experimentation this does not represent a problemgiven that one does not know yet how these SD HASCAdosage forms will behave in vivo

Decreasing the diffusion surface area using the SSP ledto a decrease in the release rate and consequently to animprovement of the similarity of the 700-mg tablet with100mg of drug to Tridural 100mg when compared with the


0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950

Once-daily with 100mg of drugOnce-daily with 200mg of drugTridural 100mgTridural 200mg

Figure 3 Cumulative percentage of tramadol hydrochloridereleased in vitro from once-daily SD HASCA formulations com-pressed using a single-stroke press machine (SSP) and once-dailycommercial formulations (◼ 700-mg tablets with 100mg of druge 800-mg tablets with 200mg of drug 998771 Tridural 100mg andX Tridural 200mg) Tests were performed with the tablets placedinside a cage 119891

2values 7066 between 700-mg tablets with 100mg

and Tridural 100mg 7980 between 800-mg tablets with 200mg andTridural 200mg 9314 between 700-mg tablets with 100mg and800-mg tablets with 200mg

same formulation compressed with the HP (1198912equal to 7066

for the SSP versus 5309 for the HP) In the same way the1198912for the 800-mg tablet with 200mg of drug compressed

with the SSP machine was relatively higher than the 1198912for

the 800-mg tablet with 200mg of drug compressed withthe HP when both formulations were compared to Tridural200mg (119891

2equal to 7980 for the SSP versus 5583 for the

HP) The 1198912between the once-daily SD HASCA with 100mg

and the once-daily SD HASCA with 200mg formulationscompressed with the SSP was 9314 much superior to thevalue between the commercial formulations that is 6967

Figure 4 shows that the release from both the 450-mgtablets with 100mg of drug and the 500-mg tablets with200mg of drug compressedwith the SSP was slower than therelease from the commercial formulations with 100mg and200mg (119891

2equal to 5452 for twice-daily SD HASCA 100mg

and Topalgic LP 100mg and equal to 5236 for twice-daily SDHASCA 200mg and Topalgic LP 200mg) The 119891

2regarding

the similarity between the twice-daily SD HASCA formula-tions compressed with the SSP (8801) and the 119891

2regarding

the similarity between commercial formulations (8506) werenearly identical The differences between the release profilesfrom the two types of twice-daily formulations commercialand SD HASCA were not an issue since the main goal ofthe present work was essential to prove the SR propertiesof the developed SD HASCA formulations and to developonce-daily and twice-daily SD HASCA formulations withsimilar release profiles for both dose strengths (100mg and200mg) and type of formulation (once-daily and twice-daily) Besides the commercial formulations were mainlya guide to remain within reliable release profiles for the12-hour and the 24-hour release formulations Therefore a

0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690

Twice-daily with 100mg of drugTwice-daily with 200mg of drugTopalgic LP 100mgTopalgic LP 200mg

Figure 4 Cumulative percentage of tramadol hydrochloridereleased in vitro from twice-daily SD HASCA formulations com-pressed with the single-stroke press machine and twice-dailycommercial formulations (X 450-mg tablets with 100mg of drug◼500-mg tablets with 200mg of drug 998771 Topalgic LP 100mg and eTopalgic LP 200mg) Tests were performed with the tablets placedinside a cage 119891


and Topalgic LP 100mg 5236 between 500-mg tablets with 200mgof drug and Topalgic LP 200mg and 8801 between 450-mg tabletswith 100mg and 500-mg tablets with 200mg of drug

strict similarity was not required between SD HASCA andmarketed formulations

As it can be observed in Figures 3 and 4 the releaseprofiles from SD HASCA tablets can be divided into twostages which are typical of hydrophilicmatrices First a bursteffect occurs This burst of drug corresponds to the rapiddissolution and release of drug from the tablet surface whilstthe viscous gel layer forms around the dry core of the matrixtablet Thereafter the release rate decreases gradually untilthe end of the dissolution process This decrease in releaserate corresponds to an increase of the diffusion pathway thatdrug molecules have to traverse owing to the progressivelyforming gel barrierThis release behaviour is characteristic ofa mainly diffusion-controlled mechanism [38]

Table 5 shows a clear decrease in the rate of drug-releasegiven by the T50 and T90 from twice-daily and once-daily SD HASCA tablets compressed using the SSP whencompared to the tablets compressed with the HP In thesame way as it was observed for the tablets compressedwith the HP the T50 was less affected by TW than theT90 when the tablets were compressed using the SSP Thein vitro release rates from the optimized twice-daily andonce-daily SD HASCA formulations were in agreement withdocumented preferred profiles [39]

34 In Vitro Release of Tramadol Hydrochloride from SDHASCATablets under Ethanolic Conditions Theresults of thein vitro release of tramadol hydrochloride from once-dailySD HASCA tablets with 100mg of tramadol hydrochlorideand from Tridural 100mg (once-daily) in a hydroalcoholicmedium with 40 ethanol performed to address safetyissues related to simultaneous administration of SD HASCA


0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Figure 5 Cumulative percentage of tramadol hydrochloridereleased in vitro from once-daily SD HASCA tablets with 100mg ofdrug and once-daily commercial formulations with 100mg of drugin a pH gradient versus a 40 ethanol hydroalcoholic medium (998771SD HASCA with 100mg in a pH gradient X Tridural 100mg in apHgradiente SDHASCAwith 100mg in a 40ethanolicmediumand ◼ Tridural 100mg in a 40 ethanolic medium)119891

2values 7066

between 700-mg tablets with 100mg of drug and Tridural 100mg inpH gradient 8851 between 700-mg tablets with 100mg of drug andTridural 100mg in a 40 ethanol hydroalcoholic medium

tablets and ingestion of alcohol are presented in Figure 5The same figure shows the release profiles from the sameformulations in a pH gradientThe rate of release of tramadolhydrochloride from SD HASCA tablets decreased underethanolic conditions when compared to the rate of releasein a pH gradient SD HASCA formed a very hard gel in thehydroalcoholic medium which retained SR properties inde-pendently of the alcoholic environment The same decline inthe rate of release was observed for Tridural 100mg The SDHASCAand the commercial formulations demonstrated verysimilar profiles (119891

2= 8851)

It has been reported that in vitro dissolution experimentsin 40 ethanol hydroalcoholic mediums over a 2-hourperiod are expected to be representative of the most extremealcoholic conditions likely to be encountered in vivo becauseof to the dilution of the ethanol in the gastrointestinal fluids[25] Yet the dissolution tests in alcohol were carried outduring a 7-hour period to better distinguish the differentdrug-release profiles between formulations and betweendissolution mediums

The decline in the release rate may be explained by apossible susceptibility of the solubility of SD HASCA the SRagent in our tablets and Contramid (a cross-linked starch)the SR agent in Tridural to high-alcohol concentrationsIndeed it has been shown that in heated aqueous solutionscontaining some alcohols including ethanol amylose pre-cipitates forming complexes known as Vh-amylose crystals[40] However in the same study where SD HASCA wasdesigned it was suggested that the presence of a Vh formof HASCA was unnecessary to obtain sustained drug-releaseand that its concentration did not influence the drug-releaseprocess as long as it remained a minor component in

a mainly amorphous matrix [6] Further studies on thecomplex interactions between ethanol and the solubility ofthe SR excipients are required to explain the slower releaserate Although the solubility of tramadol hydrochloride is pHindependent distinct solubility of tramadol hydrochloride ina pH gradient versus that in the ethanolicmedium if any willalso influence its release from the formulations

Tramadol hydrochloride is available from a number ofcompanies as once-daily SR formulations in strengths upto 300mg The higher dose in SD HASCA formulations is200mg There is a potential of dose dumping with theseformulation if they are tampered with that is cut brokecrushed chew or simultaneously administered with alcoholDose dumping could lead to harmful adverse effects likenausea dizziness vomiting headache and abdominal pain[41] Besides tramadol adverse effects are accentuated in thepresence of alcohol

The influence of ethanol on the in vitro release ofsome opioid drugs including tramadol hydrochloride froma number of SR formulations employing diverse releasetechnologies has been investigated following the withdrawnof a once-daily formulation of an opioid drug from the USmarket Studies had shown that simultaneous ingestion ofethanolmodified its release characteristics and induced dose-dumping which urged the FDA to consider the issue ofpotential and harmful changes of the release characteristicsof new and marked extended-release formulations caused byethanol ingestion [25]

The dissolution studies showed that SD HASCA tabletsformed a hard gel which maintained SR properties and wasresistant to exposure to a simulation of the pH variationsthrough the gastrointestinal tract as well as to ethanolicconditions Both SD HASCA and commercial formulationsformed a denser gel in ethanolic medium although thediameter and appearance of the formulations after 7 hoursrelease did not change much (Figure 6) Moreover themoderate cracks that appeared on the tablet surface duringthe dissolution tests in a pH gradient did not affect drug-release which suggests that the risk of undesired burst releasein vivomight be low

In fact an in vivo study where SD HASCA tabletscontaining acetaminophen and sodium chloridewere admin-istered to fasted healthy human volunteers suggested that theformed gel is strong enough to maintain its integrity whiletraversing the stomach resisting the vigorous peristalticcontractions which in the fasted state clear the stomachof any residual material (commonly known as housekeeperwaves) [16] However this in vivo study was carried out ona very small number of volunteers and thus its results haveto be considered carefully Moreover the very high crushingstrengths observed for these tablets are likely to preventpossible accidental breaking and crushing These findingssupport the value of SD HASCA as a robust excipient fororal sustained drug-release which may reduce the likelihoodof severe adverse effects that can occur in the case of anaccidental dose dumping due to misuse (breaking crushingbisection of the tablets or simultaneous alcohol ingestion) ofthe medication


(a) (b)

(c) (d)

Figure 6 700-mg tablets with 100mg of tramadol hydrochloride in (a) pH gradient and (b) 40 ethanol hydroalcoholicmedium (b) Tridural100mg in (c) pH gradient and (d) 40 ethanol hydroalcoholic medium

4 Conclusion

SD HASCA is an interesting excipient for sustained drug-release in solid oral dosage forms It is biodegradable inex-pensive and allows facile manufacturing of tablets by directcompression Tablets made from SD HASCA show indepen-dence of drug-release from CF high crushing strengths andare amenable to twice-daily and once-daily formulationsThemechanical strength of the SD HASCA gel formed when thetablets are exposed to either a pH gradient or to an ethanolicmedium suggests that these tablets are likely to withstand themechanical stresses that occur after oral administration aswell as coadministration with alcohol preventing undesireddisintegration of the tablets in the gastrointestinal tractwith consequent dose dumping Moreover the propertiesexhibited by SD HASCA tablets suggest this polymer isa promising and robust excipient for oral sustained drug-release which may possibly minimize the likelihood of dosedumping and consequent adverse effects if inadvertent ordeliberate misuse of the medication such as simultaneousingestion of alcohol occurs

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This paper is dedicated to the living memory of ProfessorLouis Cartilier Professor Cartilier was the initial instigator ofthis research project Professor Leclair assumed the scientificdirection of this project after Professor Cartilier deceased in2011 Teresa Nabais gratefully acknowledges the scholarshipsupport of Fundacao para a Ciencia e Tecnologia (Portugal)The authors also thank Jeanne Leblond Chain and all the stu-dents and members of the Group Meeting Axe Formulationfor proofreading this paper and for helpful suggestions

References

[1] J Kost and S Shefer ldquoChemically-modified polysaccharides forenzymatically-controlled oral drug deliveryrdquo Biomaterials vol11 no 9 pp 695ndash698 1990

[2] C G Biliaderis ldquoThe structure and interactions of starch withfood constituentsrdquoCanadian Journal of Physiology and Pharma-cology vol 69 no 1 pp 60ndash78 1991

[3] J M Fang P A Fowler C Sayers and P A Williams ldquoThechemical modification of a range of starches under aqueousreaction conditionsrdquo Carbohydrate Polymers vol 55 no 3 pp283ndash289 2004

[4] E Svensson and A-C Eliasson ldquoCrystalline changes in nativewheat and potato starches at intermediate water levels during


gelatinizationrdquo Carbohydrate Polymers vol 26 no 3 pp 171ndash176 1995

[5] A Rajan V S Prasad and T Emilia Abraham ldquoEnzymaticesterification of starch using recovered coconut oilrdquo Interna-tional Journal of Biological Macromolecules vol 39 no 4-5 pp265ndash272 2006

[6] F Brouillet G Baylac L Cartilier and B Bataille ldquoHigh-amylose sodium carboxymethyl starch matrices for oral sus-tained drug release development of a spray-dryingmanufactur-ing processrdquo Drug Development and Industrial Pharmacy vol36 no 7 pp 795ndash805 2010

[7] L Cartilier I Moussa C Chebli and S Buczkowski ldquoSubsti-tude amylose as a matrix for sustained drug releaserdquo US Patent5879707 1999

[8] L Cartilier M Ungur and C Chebli ldquoTablet formulation forsustained drug-releaserdquo Canadian Patent Application 2491665PCT Application no PCTCA2005001934 2005

[9] C Chebli and L Cartilier ldquoEffect of some physical parameterson the sustained drug-release properties of substituted amylosematricesrdquo International Journal of Pharmaceutics vol 193 no 2pp 167ndash173 2000

[10] S H Moghadam HWWang E S El-Leithy C Chebli and LCartilier ldquoSubstituted amylose matrices for oral drug deliveryrdquoBiomedical Materials vol 2 no 1 article S11 pp S71ndashS77 2007

[11] C Chebli I Moussa S Buczkowski and L Cartilier ldquoSubsti-tuted amylose as a matrix for sustained drug releaserdquo Pharma-ceutical Research vol 16 no 9 pp 1436ndash1440 1999

[12] M Ungur N Yonis C Chebli and L Cartilier ldquoThe evaluationof carboxymethylamylose for oral drug delivery systems fromlaboratory to pilot scalerdquo in Proceedings of the 3rd InternationalSymposium on Advanced BiomaterialsBiomechanics (ISAB2rsquo05) vol 271 Montreal Canada 2005

[13] S Edge and R W Miller ldquoSodium starch glycolaterdquo in Hand-book of Pharmaceutical Excipients R C Rowe P J Sheskey andS C Owen Eds pp 701ndash704 Pharmaceutical Press LondonUK 2005

[14] V Lenaerts I Moussa Y Dumoulin et al ldquoCross-linked highamylose starch for controlled release of drugs recent advancesrdquoJournal of Controlled Release vol 53 no 1ndash3 pp 225ndash234 1998

[15] F Brouillet B Bataille and L Cartilier ldquoHigh-amylose sodiumcarboxymethyl starch matrices for oral sustained drug-releaseformulation aspects and in vitro drug-release evaluationrdquo Inter-national Journal of Pharmaceutics vol 356 no 1-2 pp 52ndash602008

[16] T Nabais F Brouillet S Kyriacos et al ldquoHigh-amylose car-boxymethyl starch matrices for oral sustained drug-release invitro and in vivo evaluationrdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 65 no 3 pp 371ndash378 2007

[17] L J Scott and C M Perry ldquoTramadol a review of its use inperioperative painrdquo Drugs vol 60 no 1 pp 139ndash176 2000

[18] S Nossol M Schwarzbold and T Stadler ldquoTreatment ofpain with sustained-release tramadol 100 150 200mg a post-marketing surveillance studyrdquo International Journal of ClinicalPractice vol 52 no 2 pp 115ndash121 1998

[19] S Grond and A Sablotzki ldquoClinical pharmacology of tra-madolrdquo Clinical Pharmacokinetics vol 43 no 13 pp 879ndash9232004

[20] R L Barkin ldquoExtended-release tramadol (ULTRAM ER)a pharmacotherapeutic pharmacokinetic and pharmacody-namic focus on effectiveness and safety in patients with chronicpersistent painrdquo The American Journal of Therapeutics vol 15no 2 pp 157ndash166 2008

[21] P I Hair M P Curran and S J Keam ldquoTramadol extended-release tabletsrdquo Drugs vol 66 no 15 pp 2017ndash2027 2006

[22] H Malonne B Sonet B Streel et al ldquoPharmacokinetic evalu-ation of a new oral sustained release dosage form of tramadolrdquoBritish Journal of Clinical Pharmacology vol 57 no 3 pp 270ndash278 2004

[23] M Raber H U Schulz M Schurer S Krupp and H Mom-berger ldquoPharmacokinetic properties of tramadol sustainedrelease capsules 3rd communication investigation of rela-tive bioavailability under steady state conditionsrdquo Arzneimit-telforschung vol 49 no 7 pp 594ndash598 1999

[24] US Pharmacopeial Convention The United States Pharma-copeia 36mdashNational Formulary 31 Rockville Md USA 2013

[25] M Walden F A Nicholls K J Smith and G T Tucker ldquoTheeffect of ethanol on the release of opioids from oral prolonged-release preparationsrdquo Drug Development and Industrial Phar-macy vol 33 no 10 pp 1101ndash1111 2007

[26] T Durig and R Fassihi ldquoEvaluation of floating and stickingextended release delivery systems an unconventional dissolu-tion testrdquo Journal of Controlled Release vol 67 no 1 pp 37ndash442000

[27] J W Moore and H H Flanner ldquoMathematical comparison ofdissolution profilesrdquo Pharmaceutical Technology vol 20 no 6pp 64ndash74 1996

[28] M Lemieux P Gosselin and M A Mateescu ldquoCarboxymethylhigh amylose starch as excipient for controlled drug releasemechanistic study and the influence of degree of substitutionrdquoInternational Journal of Pharmaceutics vol 382 no 1-2 pp 172ndash182 2009

[29] N A Peppas and J J Sahlin ldquoA simple equation for thedescription of solute release III Coupling of diffusion andrelaxationrdquo International Journal of Pharmaceutics vol 57 no2 pp 169ndash172 1989

[30] P Colombo R Bettini P Santi and N A Peppas ldquoSwellablematrices for controlled drug delivery gel-layer behaviourmechanisms and optimal performancerdquo Pharmaceutical Scienceand Technology Today vol 3 no 6 pp 198ndash204 2000

[31] B Narasimhan and N A Peppas ldquoMolecular analysis of drugdelivery systems controlled by dissolution of the polymercarrierrdquo Journal of Pharmaceutical Sciences vol 86 no 3 pp297ndash304 1997

[32] V V Ranade ldquoDrug delivery systems 5A Oral drug deliveryrdquoJournal of Clinical Pharmacology vol 31 no 1 pp 2ndash16 1991

[33] M Lemieux P Gosselin and M A Mateescu ldquoInfluence ofdrying procedure and of low degree of substitution on thestructural and drug release properties of carboxymethyl starchrdquoAAPS PharmSciTech vol 11 no 2 pp 775ndash785 2010

[34] C Calinescu E Nadeau J Mulhbacher J M Fairbrotherand M-A Mateescu ldquoCarboxymethyl high amylose starch forF4 fimbriae gastro-resistant oral formulationrdquo InternationalJournal of Pharmaceutics vol 343 no 1-2 pp 18ndash25 2007

[35] L PMassicotteW E Baille andMAMateescu ldquoCarboxylatedhigh amylose starch as pharmaceutical excipients Structuralinsights and formulation of pancreatic enzymesrdquo InternationalJournal of Pharmaceutics vol 356 no 1-2 pp 212ndash223 2008

[36] T D Reynolds S A Mitchell and K M Balwinski ldquoInvestiga-tion of the effect of tablet surface areavolume on drug releasefrom hydroxypropylmethylcellulose controlled-release matrixtabletsrdquoDrugDevelopment and Industrial Pharmacy vol 28 no4 pp 457ndash466 2002


[37] J Siepmann H Kranz N A Peppas and R BodmeierldquoCalculation of the required size and shape of hydroxypropylmethylcellulose matrices to achieve desired drug release pro-filesrdquo International Journal of Pharmaceutics vol 201 no 2 pp151ndash164 2000

[38] YW Chien ldquoFundamentals of controlled drug administrationrdquoin Novel Drug Delivery System J Swarbrick Ed pp 465ndash574Marcel Dekker New York NY USA 1982

[39] B Oshlack H-P Huang M Chasin and P Goldenheim ldquoSta-bilized sustained release tramadol formulationsrdquo US Patent6306438 B1 2001

[40] W Helbert and H Chanzy ldquoSingle crystals of V amylose com-plexed with n-butanol or n-pentanol structural features andpropertiesrdquo International Journal of Biological Macromoleculesvol 16 no 4 pp 207ndash213 1994

[41] I Tagarro J Herrera C Barutell et al ldquoEffect of a simple dose-escalation schedule on tramadol tolerability assessment in theclinical settingrdquo Clinical Drug Investigation vol 25 no 1 pp23ndash31 2005

Submit your manuscripts athttpwwwhindawicom

PainResearch and TreatmentHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Volume 2014

ToxinsJournal of

VaccinesJournal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

AntibioticsInternational Journal of

ToxicologyJournal of


StrokeResearch and TreatmentHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Drug DeliveryJournal of



Advances in Pharmacological Sciences

Tropical MedicineJournal of


Medicinal ChemistryInternational Journal of


AddictionJournal of



BioMed Research International

Emergency Medicine InternationalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014


Autoimmune Diseases


Anesthesiology Research and Practice

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of


Pharmaceutics


MEDIATORSINFLAMMATION

of


solubility and tablet weight (TW) [7 11] and unusually highcrushing force values [10]

The use of sodium chloroacetate or chloroacetic acidin place of nonionic substituents like glycidol has beensubsequently proposed to produce an excipient more readilyacceptable by regulatory agencies for its nontoxicity [8 12]Sodium carboxymethyl starch with low-amylose content wasalready awell-knowndisintegrant agent in immediate-release(IR) tablets [13] High-amylose sodium carboxymethyl starch(HASCA where ldquoHASrdquo means high-amylose substitutedstarch and ldquoCArdquo defines the substituent used herein chloroac-etate) contrariwise has been introduced as a promisingpharmaceutical excipient for oral SR tablets prepared bydirect compression [12] Contramid a cross-linked highamylose starch has already been used in tablets as a retardingagent [14]

After being initially produced on laboratory scale thepolymer was obtained on an industrial pilot scale Howeverthese latter batches of polymer were unsuitable for tabletingand sustained drug-release due to inadequate physical prop-erties For this reason the material was spray-dried (SD) toobtain a compressible excipient This procedure which hasbeen described elsewhere [6] resulted in SD HASCA thepolymer used in the current study

Studies on the in vitro release characteristics ofacetaminophen from tablets composed of SD HASCAdrug and sodium chloride have demonstrated the suitabilityof this polymer as a sustained drug-release excipient Noburst effect was observed even in the presence of largeamounts of soluble sodium chloride in the formulation[15 16] Moreover the release of acetaminophen fromoptimized SD HASCA formulations is not significantlyinfluenced by the variations of pH and residence time inacidic media [16] These prior results suggest that drug-release from SDHASCA tablets may not be affected by intra-and intersubject variations in gastric pH or gastric residencetime Acetaminophen (phenol pKa 951) and tramadolhydrochloride (tertiary amine pKa 941) are completelynonionized and completely ionized at physiological pHrespectively Moreover a first in vivo study where the sameoptimized SD HASCA formulation was administered orallyto healthy human subjects has demonstrated extendedacetaminophen plasma levels and demonstrated that the gelformed by the polymer was strong enough to resist boththe powerful peristaltic contractions normally occurringin the fasted state and biodegradation in the intestine [16]Other features of SD HASCA that confirm the potential ofthis polymer for sustained drug-release include its excellentbinding properties in the absence of binders which resultedin very high crushing forces [6 15] A strong dependence ofdrug-release on TW has also been found corresponding to aTW rise to an increased total release time [15]

Tramadol is a synthetic centrally acting analgesic agentwith a dual mechanism of action [17] It has proven to beeffective in the treatment of moderate to moderately severepain without causing severe side effects and organ damages[18] For the treatment of chronic pain frequent oral admin-istration of IR tramadol is required (at least four times daily)because of its mean elimination half-life which can vary

from 5 to 7 h in humans [19] In adults and adolescents theusual oral dosage regimen is 50 to 100mg every 4 to 6 hourswith a maximum dosage of 400mgday [17] Consequentlyoral formulations of tramadol that provide a more gradualrelease of the drug have been developed with the aim ofreducing the frequency of administration minimizing acuteadverse effects and thus improving the patient compliance[20 21] After oral administration tramadol is rapidly andalmost completely absorbed Its bioavailability of 70 after asingle administration can be attributed entirely to extensivefirst pass metabolism [22] However at steady state thebioavailability of a SR formulation has been shown to be 100relative to an IR formulation [23] which represents anotheradvantage of SR formulations of tramadol Bioequivalenceafter dose adjustment between IR and SR formulations hasbeen demonstrated [19] Tramadol hydrochloride is readilysoluble in water and ethanol and hence judicious selectionof release retarding excipients is necessary to achieve anextended in vivo input rate of the drug

SR formulations especially those designed for once-daily administration contain amounts of drug that can bepotentially risky if released as a burst commonly called dosedumping Tramadol hydrochloride may cause severe sideeffects if high plasma concentrations are reached quicklyInadvertent or intentional misuse of a SR formulation withconsequent dose dumping may include breaking crush-ing tablets and simultaneous coingestion of the medica-tion with high doses of ethanol Therefore the robustnessof SD HASCA tablets in an ethanolic medium and theircrushing strength values are important factors to take intoaccount

In this study the in vitro release characteristics frommatrix tablets comprising tramadol hydrochloride as themodel drug and SD HASCA as the only SR excipient wereevaluated in a series of buffers simulating the pH of thefluids throughout the gastrointestinal tract Tablets intendedto twice-daily and once-daily administration were devel-oped These tablets contained 100 mg and 200 mg of drugrespectively The dissolution profiles of these tablets werecomparedwith those ofmarketed tramadol hydrochloride SRformulations of the same drug content The resistance of thegel formed by SD HASCA to an alcoholic medium was alsoinvestigated

2 Materials and Methods

21 Materials Amorphous HASCA (Eurylon 6 batch 3910ref 799511) was provided by Roquette Freres (LestremFrance) and contained approximately 60 of amylose and40 of amylopectin The DS was equal to 0045 (numberof moles of substituentnumber of moles of anhydroglucose)[15] Tramadol hydrochloride was purchased from JubilantOrganosys Ltd (Nanjangud Mysore India) Commerciallyavailable tramadol tablets Tridural 100mg and 200mgRalivia 200mg Zytram XL 200mg Topalgic LP 100mg and200mg and Contramal LP 200mg were purchased frompharmacies in Canada and in France All chemicals were ofreagent grade and were used without further purification






400



500


700


800



















2= 9977) was






1198912= 50 times log[1 + (1

119899)119899

sum119905minus1

(119877119905minus 119879119905)2

]

minus05

times 100 (1)

where 119877119895and 119879



2
























0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750














2equal to 8239)







Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of






400



500


700


800



















2= 9977) was






1198912= 50 times log[1 + (1

119899)119899

sum119905minus1

(119877119905minus 119879119905)2

]

minus05

times 100 (1)

where 119877119895and 119879



2
























0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750














2equal to 8239)







Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of









2= 9977) was






1198912= 50 times log[1 + (1

119899)119899

sum119905minus1

(119877119905minus 119879119905)2

]

minus05

times 100 (1)

where 119877119895and 119879



2
























0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750














2equal to 8239)







Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of



















0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750














2equal to 8239)







Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of







0

20

40

60

80

100

0 4 8 12 16 20 24

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)610 1570600 1950640 1160750














2equal to 8239)







Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of





Topalgic LP100mg

Topalgic LP200mg

Contramal LP200mg

100mgof drug (SSP)

200mgof drug (SSP)

[215 760] [200 690] [210 685] [300 1070] [300 1025]








1 [390 1425] 9015 [410 1450] 892 [425 1540] 8425 [400 1440]
























0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of

















0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of


0

20

40

60

80

100

0 4 8 12 16 20 24 28 32

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)520 2040520 1910610 1570600 1950















2regarding


2regarding


0

20

40

60

80

100

0 4 8 12 16 20

Qua

ntity

of d

rug

rele

ased

()

Time (h)

Formulation T50 T90 (h)300 1070300 1025215 760200 690










0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of


0

10

20

30

40

50

60

0 1 2 3 4 5 6 7 8

Qua

ntity

of d

rug

rele

ased

()

Time (h)


2values 7066



2= 8851)









(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of


(a) (b)

(c) (d)


4 Conclusion




Acknowledgments


References

















































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of













































Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of











Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of





Volume 2014

ToxinsJournal of

VaccinesJournal of















AddictionJournal of






Autoimmune Diseases




Journal of


Pharmaceutics



of

Documents

High-Amylose Sodium Carboxymethyl Starch Matrices