Analgesics · Anti-inflammatories · Antiphlogistics · Antirheumatic Drugs

Comparative in vitro dissolution and in vivo bioequivalence of two diclofenac enteric coated formulations

Saeed Basmenji\ Hadi Valizadeh2•3

, Parvin Zakeri-Milani3•4

1 Daana Pharmaceutical Company, Tabriz, Iran 2 Research Center for Pharmaceutical Nanotechnology, Tabriz University of Medical Scien ces, Tabriz, Iran 3 Department of Pharmaceutics, Faculty of Pharmacy, Tabriz Un iversity of Medical Scien ces, Tabriz, Iran 4 Liver and Gastrointestinal Diseases Research Center, Tabriz University of Medical Scien ces, Tabriz, Iran

Correspondence to: Parvin Zakeri-Milani, PhD, Associate Professor of Pharmaceutics, Faculty of Pharmacy,

Tabriz University of Medical Sciences, Tabriz, 51664, Iran; e -mail: p zakeri@tb=ed.ac. ir

Abstract

The aim of this study was the comparison of in vitro dissolution and in vivo bioa­vailability of two different brands of di­clofenac sodium (CAS 15307-86-5) enteric coated tablets in healthy male Iranian volunteers in a single-dose, randomized, open-label, single blind study, which was conducted according to a crossover design in healthy volunteers. A washout interval of two weeks was selected between administrations to each subject in this study. Serial venous blood samples over 10 h after each administration to measure diclofenac sodium concentra­tion in serum were obtained, and placed into tubes containing sodium heparin. Then the plasma was separated and kept frozen at -20 oc for subsequent analysis with a modified HPLC method with UV

detection. In addition, the in vitro dissolution study was performed on the

1. Introduction

brands. For the test and reference formulation, mean Cmax values were 2257.3 (ng/rnl) and 2156 (ng/rnl), respec­tively. The mean AUG~ and A UG i)' were 5726.1 (ng · h/rnl) and 5917.8 (ng · h/rnl) for the test and 5689.9 (ng · h/rnl) and 5967.4 (ng · h/rnl) for the reference for­mulation, respectively. Results show that the 90 % confidence intervals for the ratio of test and reference products in Cmax (101.4-114.9 %) , AUG~ (96.3 -109.1 %)

and AUGO' (94.7-107.3 %) were all within the 80-125% interval proposed by the FDA and EMA. Both formulations re­leased > 80 % of drug within 30 min in buffer pH = 6.8 medium. Therefore the diclofenac sodium enteric coated tablets of the test and reference formulations are bioequivalent in terms of rate and extent of absorption.

Keywords

• Bioavailability • Bioequivalence • Diclofenac • Dissolution

Arzneimittelforschung 2011;61(10):566-570

Non-steroidal anti-inflammatory drugs (NSAIDs) are the drugs most commonly used to reduce inflammation and pain. NSAIDs inhibit cyclooxygenase-2 at the inflamma­tion, but unfortunately most of them inhibit gastric mu­cous cyclooxygenase-1, which produces gastric damage. Diclofenac sodium or, sodium [o-(2,6-dichloro-phenyl)­amino-phenyl] acetate (CAS 15307-86-5) is a non-selec­tive cyclooxygenase 1 and 2 inhibitor when tested in vi­tro, but a slightly preferential cyclooxygenase-2 inhibi­tor when tested ex vivo [1, 2]. It is approved for long term therapy in patients with osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, acute gout, following some surgical procedures and soft-tissue inflammation in dosages ranging from 75 to 150 mg/day, depending

on the indication. Diclofenac sodium is well absorbed orally and dissolves in the intestinal fluid [3]. It is gener­ally known that the drug gets into blood within 30 min and reaches the maximum blood concentration CCmax) within 1.5- 2.5 h following oral administration of an en­teric coated tablet. The oral bioavailability is around 60 % with an excretion half-life between 1.1 and 1.8 h [4]. Diclofenac sodium is characterized by rapid sys­temic clearance, which necessitates two or three daily doses [5]. There are substantial evidences that the meth­od of manufacture and the final formulation of the drug can markedly affect the bioavailability of the drug. On the other hand there are several drug products contain­ing the same amount of diclofenac sodium marketed by different pharmaceutical manufacturers. In fact the World Health Organization (WHO) and all drug regula-

566 Basmenji eta!. - Diclofenac Arzneimittelforschung 2011;61(10):566-570

© ECV · Editio Cantor Verlag, Aulendorf (Germany)

tory agencies support commercialization of generic medicines because they control costs and are irreplace­able therapeutic options in countries lacking the inno­vator product [6]. However, it is necessary to examine brand drug products in regard to in vitro dissolution and in vivo bioequivalence, and interchangeable uses with the innovator product. Therefore in the present study in vitro dissolution behavior and also the rate and extent of absorption of two commercial brands of enteric coated tablets of diclofenac sodium were deter­mined and compared following oral administration in healthy Iranian volunteers.

2. Methods

2.1 In vitro dissolution study A comparative in vitro dissolution study was conducted ahead of the in vivo bioequivalence studies according to the procedure described in the US Pharmacopeia. It was ensured that the in vi­tro dissolution data were acceptable as per the regulatory guide­lines for conducting bioequivalence studies. The dissolution study was carried out on 12 units each of the test and reference formulations. The paddle rotation speed was maintained at 100 rotations per minute at 37 ± 0.5 °C. The test was carried out using 900 mL of 0.1 N HCl for 1 h followed by pH 6.8 phosphate buffer for the next hour as dissolution media. Samples of 5 ml were withdrawn at predetermined time intervals (30, 60, 65, 70, 75, 90, 105 and 120 min and replaced with the same volume of fresh buffer. Each sample solution was filtered, diluted and the absor­bance reading determined at 276 nm using a spectrophotometer (Shimadzu 160, Kyoto, Japan) against the blank. The concentra­tions were thereafter determined from the calibration curve. The mean dissolution values at each time interval were used to calcu­late the difference factor (f1) and similarity factor (fzl using the standard mathematical equations [7,8]:

f2 =50 x log {[1 + (1/n) :E~1 (R, - T,) 2r 05 x 100}

f1 = {[L,';,!IRr - Tdl I [~I R,]} X 100

where n is the number of dissolution sample times, R, and T, are the individual or mean percent dissolved at each time point, and t stands for the reference and test dissolution pro­files, respectively.

2.2 Subjects and study design

In this investigation 24 male healthy volunteers were recruited with informed consent in an open label, single-dose, rando­mized study with a crossover design and a washout period of two weeks between the two phases in accordance with the guidelines of the Declaration of Helsinki (World Medical As­sembly 1964) as last revised in Seoul (2008). The study protocol was approved by the local ethics committee of Tabriz Univer­sity of Medical Sciences, Iran. Subject selection was according to certain established criteria for inclusion into or exclusion from the study. For examples any volunteers being smokers, having allergies to the drug, being overweight or taking any other medications prior to the study were excluded. Two brands of diclofenac sodium enteric coated tablets were se­lected as a reference (batch no. UOOll) and test (Exir Pharma­ceutical Co, Boroujerd, Iran, batch no. 059-01 06) formulations. Subjects were all Iranians and their average age and weight were 23.2 ± 1.6 years and 67.3 ± 8.6 kg, respectively. They were

Arzneimittelforschung 2011;61(10):566-570 © ECV . Editio Cantor Verlag, Aulendorf (Germany)

Analgesics . Anti-inflammatories · Antiphlogistics · Antirheumatic Drugs

examined for their health conditions. Two tablets (equivalent to 25 mg diclofenac sodium) of the test and the reference for­mulations were randomly given to the volunteers. Seven milli­liters of blood taken from subject's forearm veins serially at 0, 0.5, 1, 1.5, 2, 3, 4, 6, 8, and 10 h after each administration. All blood samples were collected into heparinized tubes and plas­ma samples were separated and kept frozen at a temperature below - 20 oc for subsequent analysis.

2.3 Plasma sample analysis In different studies many methods for determination of diclofe­nac sodium plasma concentrations were utilized. Among them validated high-performance liquid chromatography (HPLC) either with UV [1, 9], fluorimetric [2], or electro-chemical detec­tion [1 , 3, 5, 10-17]; gas chromatography- mass spectrometry [ll] and thin-layer chromatography (TLC) [5] have been re­ported. In this study the analytical procedure for determination of diclofenac sodium in plasma was adopted from the method of El-Sayed and co-workers and validated for specificity, accuracy, precision and sensitivity [18]. For extraction of diclofenac so­dium, on 1 ml of plasma 50 JlL of the internal standard (200 Jlgl m1 ofnaproxen) and 200 JlL ofHCI1 Nwas added, then all sam­ples were extracted with 5 ml hexane/ isopropyl alcohol (99 I 1) by vortexing for 5 min. After centrifugation for 5 min at 1000 g, the upper organic phase was transferred to a 7 ml glass evaporation tube. The tubes were placed in a 45 oc water bath. After dryness the residue reconstituted with 200 JlL of the mobile phase by vor­tex mixing for 20 s. 150 JlL of the resulting solution was injected onto the HPLC column. The mobile phase was a mixture of acet­onitrile and water (45: 55% v/v), pH= 3.3 adjusted with acetic acid. The analytical column used for chromatographic separa­tions was Shim pack CLC C18, 5 Jlm (150 x 4.6 mm) with a Shim­pack CLC-C18, 5 Jlm 4.6 x 20 mm guard column (Shimadzu, Kyoto, Japan) . The flow rate was 2 ml/min and the detector wa­velength was set at 282 nm. Under these conditions the retention times for diclofenac sodium and the internal standard (naprox­en) were 4.2 and 2.3 min respectively. All plasma samples were measured in the same chromatographic run. Each run had a se­parate daily calibration. Four quality control samples with con­centrations within the calibration range were used in triplicates (n = 3) to determine the accuracy and precision of the method [ 19, 20]. Calibration curves were obtained by plotting the diclofe­nac sodium to naproxen peak area ratio against the concentra­tions of the standard solutions.

2.4 Data analysis The plasma concentration-time data for each volunteer was presented in a graphical form. For oral dosage form, the bioa­vailability of the drug is most often described by measuring the area under the plasma drug concentration-time curve (AUC), the time for peak drug concentration, Tmro<> and the peak drug concentration, Cmax· The area under the plasma concentration­time curve from time zero tot (AUCb), AUC ~, AUCO' and (t112l were calculated as previously described [21 -28] .

3. Results and discussion 3.1 In vitro dissolution study

Dissolution curves are shown in Fig. 1. From the disso­lution profiles, it is clear that there were almost no drug release from both enteric coated formulations in the acidic medium as expected. However, in the phosphate buffer medium (pH 6.8), more than 80 % of drug was re-

Basmenji et al. - Diclofenac 567

Analgesics · Anti-inflammatories . Antiphlogistics · Antirheumatic Drugs

HCI0.1N Phosphate bufferpH=6.8

100

80

~

"' 60 ., > ~ V>

i:5 40

20

0

0 20 40 60 80 100 120

Time(min)

Fig. 1: Dissolution profiles of diclofenac sodium. Open and solid circles are the data for reference and test formulations, respectively.

leased within the first 30 min. Moreover the difference factor (f1) of 10.8 (acceptable limit 0- 15) and the simi­larity factor (f2) of 57.7 (acceptable limit 50-100) were calculated [8]. A comparative in vitro dissolution study provides a basis for predicting the likelihood of achiev­ing a successful in vivo bioequivalence performance. This in vitro dissolution study showed that the test and reference formulations were comparable, indicating in­terchangeability of the two brands.

3.2 Method validation

This analytical method was linear in the 10 to 4000 ng/ ml range; with a coefficient of correlation (r) greater

0.4

0.3

0.3

1 0.2 .,.

~ = 0.2 ., 0

~ -~ 0 .,. ~ A

0.2 0 g ~ u 2 ..., !2

~ ~ ~ {/) i5 ....; .;! 0.1 ~ ~

.£

I .~

i5 Q

I : I 0.0

0.0

llt~fl1 ~~ ~ 0.0 I

15 20 25 30

;a

than 0.99 and sensitivity CLOD) of 5 ng/ml of diclofenac sodium in plasma. The recovery of diclofenac sodium was 81.54, 88.5, and 90.1% at a concentration of 20, 200, and 1000 ng/ml, respectively. Recovery values for the extraction procedure were calculated by comparing chromatographic responses obtained from spiked ex­tracted plasma and drug free plasma samples spiked with the same concentration immediately after extrac­tion. Recovery of the internal standard was 92 %. More­over the intra-assay accuracy of the method ranged from 97.6 to 99 %, while the inter-assay accuracy ranged from 100.4 to 104.7%. A representative chromatogram of different diclofenac sodium standard concentrations in plasma samples is shown in Fig. 2.

3.3 Pharmacokinetic study

The mean concentration-time plots after administration of reference and test formulations to 24 healthy volun­teers are shown in Fig. 3. In Table 1, the averages of pharmacokinetic parameters after administration of both formulations to 24 subjects are reported. The mean maximum serum concentrations of 2257.3 (ng/ml) and 2156.4 (ng/ml) were obtained for the test and reference formulation, respectively. In only three volunteers a sec­ond peak phenomenon was observed which can be at­tributed to diclofenac transformation to the tetrahydrate with lower solubility [29]. The respective values for T max•

were 2.13 hand 2.21 h, and the amount of the AUC& and AUC0 for the test formulation were 5723.1 (ng · h/ml) and 5917.8 (ng · h/ml) respectively, the obtained values for the reference formulation were 5689.9 (ng · h/ml) and 5967.4 (ng · h/ml), respectively.

.40

~ .36

~' 0 0 0 M .32 )l g £ =:

i. u ~ .28 ~ Q

0 ~

1 <> 0

~ .24 "'·

I .20 ;a ;a !2

.16

.12

~\ .08

.04

.00

35 40 45 50 Minutes

Fig. 2: Representative chromatogram of different diclofenac sodium standard concentrations in plasma samples.

568 Basmenji et a!. - Diclofenac Arzneimittelforschung 2011;61(10):566-570

© ECV · Editio Cantor Verlag, Aulendorf (Germany)

Analgesics · Anti-inflammatories · Antiph logistics · Antirheumatic Drugs

Fig. 3: Average(± SD) plasma concentration of diclofenac sodium versus time plots of 24 subjects after administration of 25 mg diclofenac sodium tablets of test and reference formulations. Top: linear scale, bottom: log-linear scale.

Table 1: Diclofenac Tmax, Cmroo AUC~, AUC~, T112 values following administration of test and reference formulations to 24 healthy volunteers.

Test formulation Reference formulation Parameters

Mean (±SD) %CV Mean (±SD) %CV

Cmax (ng ml 2257.3 (± 254.5) 11.3 2156.4 (± 433.2) 20.1

Tmax (h) 2.13 (± 0.34) 15.9 2.21 (± 0.41) 18.8

AUCb (ng · h / rnl) 5723.1(± 1106.2) 19.3 5689.9 (± 1198.8) 21.1

AUCQ' (ng · h/ml) 5911.8 <= 1176.6) 19.9 5967.4 (± 1228.7) 20.6

T112 (h) 1.88 <= 0.49) 26.0 2.17 (± 0.51) 23.7

Table 2: Analysis of variance (AN OVA) for the assessment of the product, group and period effects, and 90 % confidence intervals (90% Cl) for the ratio of Cmroo AUC~ and AUC~ values for the test and reference formulations, after administration of reference and test products to 24 healthy volunteers (a= 0.05).

ANOVA (P-value)

Pharmacokinetic Variation source

90 % CI for the parameter ratios

Product Group Period

Cmax 0.3094 0.7176 0.4783 101.4- 114.9

AUCb 0.8884 0.4269 0.0903 96.3- 109. 1

AUCQ' 0.8347 0.4347 0.456 94.7 - 107.3

Arzneimittelforschung 2011;61 (10) :56&-570 © ECV · Editio Cantor Verlag, Aulendorf (Germany)

3.4 Statistical analyses

Because of the variability inherent in human subjects, pharmacokinetic parameters were analyzed statisti­cally. On the other hand a statistical confidence interval was used to pro­vide an estimated range that is likely to contain the mean pharmacoki­netic value if the drug was given to the entire population [30, 31]. There­fore in the present study, bioequiva­lence between the formulations was determined by calculating 90% con­fidence intervals (90% C. I.) for the ra­tio of Cmax• AUC~, and AUC0 values for the test and reference formula­tions [24, 32] . The multivariate analy­sis, accomplished through analysis of variance (ANOVA), was used to assess group and period effects, and values are shown in Table 2. These were all inside the acceptance limits for bio­equivalence (80 %-125 %) and there­fore the results supported the bio­equivalence. On the basis of FDA and EMA guidelines, the recently ac­cepted criterion for bioequivalence for most dosage forms requires that the mean pharmacokinetic param­eters of the test dosage form should be within 80% to 125% of the refer­ence dosage form using the 90% con­fidence interval. Thus, from the re­sults obtained it is evident that the diclofenac sodium enteric coated ta­blets of test and reference formula­tions are bioequivalent in terms of rate and extent of absorption. There­fore they are expected to have the same safety and efficacy profiles when administered under the condi­tions listed in the product labeling.

4. Conclusion The in vitro dissolution study indi­cated suitability of the test formula­tion for use in the in vivo bioequiva­lence studies. The in vivo studies in healthy human subjects demon­strated that the generic enteric coated test tablet, diclofenac so­dium 25 mg, is bioequivalent to the reference formula in terms of rate and extent of absorption.

Conflict of Interest

This study was sponsored by Exir Phar­

maceutical Co, Boroujerd, Iran. The

authors report no conflicts of interest in

this work.

Basmenji et al . - Diclofenac 569

Analgesics · Anti -inflammatories · Antiph logistics · Antirheumatic Drugs

References [1] Escribano E, Calpena AC, Queralt J, Obach R, Domenech J.

Assessment of diclofenac permeation with different formu­lations: anti-inflammatory study of a selected formula. Bur J Pharm Sci. 2003;19(4):203 - 10.

[2] Gabard B, Ellgehausen P. Comparative clinical trial with immediate-release diclofenac pellets, 50 mg tid, and slow­release diclofenac pellets, 75 mg bid. Curr Ther Res. 1993; 54(2):152 - 60.

[3] Hosny EA, Al-Helw AARM. Effect of coating of aluminum carboxymethylcellulose beads on the release and bioavail­ability of diclofenac sodium. Pharm Acta Helv. 1998;72(5):

255-61.

[4] Ayhan S, Yalcin 0, Askin I. Preparation and in vitro evalua­tion of sustained release tablet formulations of diclofenac sodium. Farmaco. 2005;60(2):171 - 7.

[5] Biasi G, Canova N, Palazzini E, Marcolongo R. Comparative pharmacokinetic study of a single dose of two prolonged­release formulations of diclofenac in healthy subjects. Curr Ther Res. 1998;59(11):785 - 92.

[6] WHO /DMP /RGS. Marketing authorization of pharmaceuti­cal products with special reference to multisource (generic) products: a manual for a drug regulatory authority. Geneva, Switzerland: World Health Organization; 1998.

[7] Esimone CO, Okoye FB, Onah BU, Nworu CS, Omeje EO. In vitro bioequivalence study of nine brands of artesunate ta­blets marketed in Nigeria. J Vector Borne Dis. 2008;45(1):60-5.

[8] Note for guidance on the investigation of bioavailability and bioequivalence. The European agency for the evalua­tion of medicinal products. London: Committee for Pro­prietary Medicinal Products; 2001.

[9] El-Samaligy MS, Yahia SA, Basalious EB. Formulation and evaluation of diclofenac sodium buccoadhesive discs. Int] Pharm. 2004;286(1 - 2):27 - 39.

[10] Su SF, Chou CH, Kung CF, Huang JD. In vitro and in vivo comparison of two diclofenac sodium sustained release oral formulations. Int J Pharm. 2003;260(1):39 - 46.

[11] Arcelloni C, Lanzi R, Pedercini S, Molteni G, Permo I, Pon­tiroli A, et al. High-performance liquid chromatographic determination of diclofenac in human plasma after solid­phase extraction. J Chromatogr B Biomed Sci Appl. 2001; 763(1-2):195 - 200.

[12] Giagoudakis G, Markantonis SL. An alternative high-per­formance liquid-chromatographic method for the determi­nation of diclofenac and flurbiprofen in plasma. ] Pharm Biom Anal. 1998;17(4- 5):897 - 901.

[13] Oberle RL, Das H, Wong SL, Chan KK, Sawchuk RJ. Phar­macokinetics and metabolism of diclofenac sodium in Yu­catan miniature pigs. Pharm Res. 1994;11(5):698-703.

[14] Lissy M, Stiff DD, Kowalski MM, Moore KA. Single-dose pharmacokinetic study of rapidly dispersing diclofenac po­tassium formulations in healthy volunteers. Curr Med Res Opin. 2009;25(10):2423-8.

[15] Leon-Reyes MR, Castaneda-Hernandez G, Ortiz MI. Phar­macokinetic of diclofenac in the presence and absence of glibenclarnide in the rat. ] Pharm Pharm Sci. 2009;12(3): 280 - 7.

[16] Ahmad M, Iqbal M, Murtaza G. Comparison of bioavail­ability and pharmacokinetics of diclofenac sodium and di­clofenac potassium in normal and dehydrated rabbits . Yao Xue Xue Bao. 2009;44(1):80 - 4.

[17] Cui Y, Lin X, Guan TT, Zhang Y, Tang X. A new rapid ultra­performance liquid chromatography method for the phar-

570 Basmenji et al. - Diclofenac

macokinetic and bioavailability study of diclofenac sodium aqueous injection and lipid microsphere injection in rats. Biomed Chromatogr. 2010;24(4):406 - 12.

[18] El-Sayed YM, Abdel-Hameed ME, Suleiman MS, Najib NM. A rapid and sensitive high-performance liquid chromato­graphic method for the determination of diclofenac so­dium in serum and its use in pharmacokinetic studies. ] Pharm Pharmacal. 1988;40:727 -9.

[19] Valizadeh H, Zakeri-Milani P, Islambulchilar z, Tajerzadeh H. A simple and rapid high-performance liquid chromato­graphy method for determining furosemide, hydrochloro­thiazide, and phenol red: applicability to intestinal perme­ability studies. J AOAC Int. 2006;89(1):88 - 93.

[20] Zakeri-Milani P, Barzegar-Jalali M, Tajerzadeh H, Azarmi Y, Valizadeh H. Simultaneous determination of naproxen, ke­toprofen and phenol red in samples from rat intestinal per­meability studies: HPLC method development and valida­tion. J Pharm Biomed Anal. 2005;39(3-4):624-30.

[21] Fujii A, Yasui-Furukori N, Nakagami T, Niioka T, Saito M, Sato Y, et al. Comparative in vivo bioequivalence and in vitro dissolution of two valproic acid sustained-release for­mulations. Drug Design Develop Ther. 2008;(2):139 - 44.

[22] Dutta S, Reed RC, Cavanaugh JH. Pharmacokinetics and safety of extended-release divalproex sodium tablets: Morning versus evening administration. American Journal of Health-System Pharmacy 2004;61(21):2280 - 2283.

[23] Dutta S, Zhang Y, Lee LL, O'Dea R. Comparison of the bioavailability of 250 and 500 mg divalproex sodium ex­tended-release tablets in healthy volunteers. Biopharm Drug Dispos. 2004;25(8):353 - 7.

[24] Zakeri-Milani P, Valizadeh H, Ghanbarzadeh S, Nemati M. Pharmacokinetics and comparative bioavailability study of two clarithromycin suspensions following administration of a single oral dose to healthy volunteers. Arzneimittel­forschung. 2009;59(8):429 - 32.

[25] Zakeri-Milani P, Valizadeh H, Islambulchilar Z, Nemati M. Pharmacokinetic and bioequivalence study of two brands of valsartan tablets in healthy male volunteers. Arzneimit­telforschung. 2010;60(2):76 - 80.

[26] Valizadeh H, Barghi L, Jalilian H, Islambulchilar Z, Zakeri­Milani P. Bioequivalence of fexofenadine tablet formula­tions assessed in healthy Iranian volunteers. Arzneimittel­forschung. 2009;59(7):345 - 9.

[27] Valizadeh H, Nemati M, Hallaj-Nezhadi S, Ansarin M, Za­keri-Milani P. Single dose· bioequivalence study of alpha­methyldopa tablet formulations using a modified HPLC method. Arzneimittelforschung. 2010;60(10):607 -11.

[28] Islambulchilar Z, Valizadeh H, Zakeri-Milani P. Rapid HPLC determination of pioglitazone in human plasma by protein precipitation and its application to pharmacoki­netic studies. J AOAC Int. 2010;93(3):876 - 81.

[29] Marzo A, Reiner V. Open questions on bioequivalence: the case of multiple peak phenomenon. ] Pharm Pharmacal. 2004;56(2) :281 - 2.

[30] Shargel L, Wu-Pong S, Yu A. Applied Biopharmaceutics &

Pharmacokinetics. New York: McGraw-Hill; 2004. [31] Krishna R, Yu L, editors. Biopharmaceutics Applications in

Drug Development New York: Springer Science+ Business

Media; 2008. [32] Zakeri-Milani P, Valizadeh H, Islambulchilar Z. Compara­

tive bioavailability study of two cefixime formulations ad­ministered orally in healthy male volunteers. Arzneimittel­forschung. 2008;58(2):97 - 100.

Arzneimittelforschung 20 ll ;61(10):566-570 © ECV · Editio Cantor Verlag, Aulendorf (Germany)