the influence of different polymers on the pharmaco-technological

FARMACIA, 2010, Vol.58, 3

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THE INFLUENCE OF DIFFERENT POLYMERS ON THE PHARMACO-TECHNOLOGICAL CHARACTERISTICS OF PROPICONAZOLE NITRATE BIOADHESIVE OROMUCOSAL TABLETS ANDREEA STANESCU1, LACRAMIOARA OCHIUZ2, ILEANA COJOCARU2, IULIANA POPOVICI2*, DUMITRU LUPULEASA1 1 The University of Medicine and Pharmacy ”Carol Davila” Bucharest, The Faculty of Pharmacy, 6, Traian Vuia Street, 020956, Bucharest, Romania 2 The University of Medicine and Pharmacy ”Gr. T. Popa”, Iasi, The Faculty of Pharmacy, 16, University Street, 700115, Iasi, Romania ∗corresponding author: [email protected]

Abstract The objective of this study is the formulation, the preparation and determination

of the physical quality parameters of the 1.5% propiconazole nitrate biomucoadhesive oral tablets, based on the reticulated polymers of the acrylic acid and hydroxypropyl cellulose, with or without chitosane, as hydrophilic polymers with optimal bioadhesive properties. There have been studied and prepared 8 formulas: F1-F4 contain 20% hydrophilic polymers: Carbopol 71, Carbopol 974, Carbopol 934, or hydroxypropyl cellulose (HPC-H); F5-F8 are similar formulas to the first four, but with 6% chitosane. The formulations with Carbopol 974, 934 and those that contain chitosane needed the addition of lubricants to improve the flow properties of the powder mixture. The results of the pharmaco-technical characterizations of the tablets have confirmed the flowing properties and the compressibility of the studied formulations. After a direct compressing process we obtained tablets with variations within the limits of 10th Romanian Pharmacopoeia and U.S.P. 32 (United States Pharmacopeia) for mass uniformity, diameter, thickness, hardness, friability and disintegration time. The swelling degree and the contact surface decreased, depending on the type of the polymer used, as follows: C974 > C934 > HPC- H > C71. The formulations with chitosane associated proved a superior swelling degree during the first 2-3 hours and also the best biomucoadhesion times, due to the bioadhesive properties of the chitosane. The pH acid values at the surface of the tablets recommend the use in the formulation of a buffer in order to assure a pH value close to the physiologic values, thus preventing the irritative effect at the aplication site.

Rezumat Obiectivul acestui studiu a constat în formularea, prepararea şi determinarea

parametrilor fizici de calitate ai comprimatelor biomucoadezive cu nitrat de propiconazol 1.5% pe bază de polimeri reticulaţi ai acidului acrilic şi hidroxipropilceluloză, asociaţi sau nu cu chitozan, ca polimeri hidrofili cu proprietăţi bioadezive optime. Au fost preparate şi studiate opt formule: F1 – F4 conţin 20% polimeri hidrofili: Carbopol 71, Carbopol 974,


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Carbopol 934 sau hidroxipropilceluloză (HPC-H); F5 – F8 sunt formule similare primelor patru având în plus 6% chitozan. Formulările pe bază de Carbopol 974, 934 şi cele care conţin chitozan au necesitat adaosul de lubrifianţi pentru îmbunătăţirea proprietăţilor de curgere a amestecului de pulbere. Rezultatele caracterizărilor farmaco-tehnice ale comprimatelor au confirmat proprietăţile de curgere şi compresibilitate ale formulărilor studiate. În urma procesului de comprimare directă am obţinut comprimate cu variaţii în limitele F.R. X şi U.S.P. XXXII pentru uniformitatea masei, diametru, grosime, rezistenţă mecanică, friabilitate şi timp de dezagregare. Gradul de îmbibare şi suprafaţa de contact au scăzut, dependent de tipul de polimer utilizat, în următoarea ordine: C974 > C934 > HPC-H > C71. Formulările în care s-a asociat chitozan au prezentat un grad de îmbibare superior în primele 2-3 ore şi cei mai buni timpi de mucobioadeziune datorită proprietăţilor bioadezive ale chitozanului. Valorile acide ale pH-ului suprafeţei comprimatelor recomandă introducerea în formulă a unui sistem tampon pentru a asigura un pH cât mai apropiat de cel fiziologic, prevenind astfel efectul iritativ la nivelului locului de aplicare.

Keywords: bioadhesion, oromucosal tablets, propiconazole nitrate, pharmaco-

technical control. Introduction The pharmaceutical biomucoadhesive forms oromucosally

administrated for a local action represent a primar issue for researchers from the drug field, due to both the various advantages that they offer in the optimization of the release kinetics of the drug substance and also because they increase the local efficacy of the therapy in the oral cavity diseases [1].

Generally, dosage forms designed for buccal drug delivery should be small and flexible enough to be acceptable for patients, non-irritating and should not interfere with normal functions such as talking, drinking and eating. Other desired characteristics of a buccal biomucoadhesive dosage form include high drug loading capacity, controlled drug release, unidirectional release, good bioadhesive properties, smooth surface, tastelessness, and convenient application [2].

Propiconazole, 1–[[2–(2,4–dichlorphenyle)–4–propyl–1,3–dioxolan–2–yl]–methyl]–14–1,2,4–triazole (fig. 1), is a triasolic-derived substance with antifungal action, synthesized in 1979, by Janssen Pharmaceuticals, Belgium.

Figure 1

Propiconazole – chemical structure


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At first, this substance has been used in agriculture as a systemic foliar fungicide, nowadays beeing used for the fungistatic action when treating mycoses differently localised.

It was observed that the propiconazole molecule binds to the fatty acids and the phospholipids present at the fungus membrane level, specifically inhibiting certain enzymes like: cytochrome C, peroxidase and catalase. All of these mechanisms determine a potent fungistatic activity of propiconazole against a wide spectrum of fungi including Candida species that resist to other antifungal agents [4-7].

The aim of this study is the formulation, preparation, physico-chemical characterization of the 1.5% propiconazole nitrate matrix biomucoadhesive buccal tablets based on hydroxypropyl cellulose H or different sorts of carbopols, with or without chitosane.

Materials and methods

Materials Propiconazole (CHWAY Chemicals & Pharmaceuticals LTD.,

China), propiconazole nitrate, has been synthesized in collaboration, using an original method, in the laboratories of the Faculty of Pharmacy from the ”N. Tetemitanu” State University, Chisinau, the Republic of Moldavia, and the University of Medicine and Pharmacy ”Gr. T. Popa” Iasi; Carbopol 71 P NF (C 71), Carbopol 974 P NF (C 974) and Carbopol 934 P NF (C 934) (Lubrizol, U.S.A.); Hydroxypropyl cellulose H (HPC-H, Nisso, Japan, viscosity degree 1.000–4.000 mPa·s); Chitosane high molecular weight (CHT) (degree of deacetylation > 85 %, Sigma Aldrich, Germany), MicroceLac 100 (Meggle GmbH, Germany); Aerosil 200 (Degussa, Germany); magnesium stearate (Union Derivan S.A Spain); flavour enhancer (Signet Chemical Corporation Pvt. Ltd., India). All used materials had the purity degree according to the regulations in force.

Methods Formulation and preparation of biomucoadhesive oral tablets:

There have been formulated eight formulas of 1.5% propiconazole nitrate bioadhesive tablets: three Carbopol formulas with different levels of crosslinker (C 71, C 974 şi C 934), named F1, F2, F3 and a formulation F4, based on HPC-H. The percent of matrix forming polymer has been the same in all the formulations, respectively 20%. In parallel, there have been formulated other four formulations where, next to the previously mentioned polymers, we also introduced CHT, 10% (F5 – F8). The MicroceLac, the


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excipient of the studied formulations, was a mixture of lactose monohydrate and microcristalline cellulose 3:1, a new generation excipient designed for direct compression with flowing and compressibility optimal properties [8 - 9]. The powders have been sieved through the TGL 7354/TGLO 4188 (150-400 µm) sieves system, and after that mixed at a constant speed, for 15 minutes. The tablets were obtained by the direct compression of the powders mixture using a Korsch EK0 monopost tabletting machine, (the dimension of the flat punch φ = 12 cm), at a 5-6 kN compression pressure, which corresponds to a 2-2.5 cm hight of the superior punch.

The determination of the flowing and compressibility properties of the powders mixture Before the compression stage, for every formulation there have been determined the following parameters [10]:

• flowing time (t) – by registering the time necessary for a 50 g powder mass to flow through a funnel having a 10 mm eyelet;

• friction coefficient (tg α) –through the dinamic method, according to the equation: tg α = h/r (1) where: h –hight and r –powder cone beam;

• angle of rest (α) –the dinamic method; • Hausner ratio (RH) – calculated by determining the density before

and after the compression, according to the equation: RH = ρt/ρi (2) where: ρt – the density after the compression and ρi – initial density;

• Carr index (IC) – identical determinations and adnotations with the ones presented at the Hausner ratio, but calculated according to the equation: IC = [ρt – ρi/ ρt]·100 (3)

The pharmaco-technical control of the bioadhesive tablets has been

performed by the determination of the following quality parameters: mass uniformity: according to the10th Romanian Pharmacopoeia, by

weighing individually the 20 tablets and by calculating the standard deviation percentage [11];

hardness, thickness, diameter: according to the 5th European Pharmacopoeia, using the Schleunger device;

friability: according to the 5th European Pharmacopoeia, using the EF II friabilator [12];


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disintegration time: according to the USP 32 [13]; the pH at the surface of the tablets has been investigated in order

to evaluate the potential irritation at the oral mucosa level, taking into consideration the prolonged contact time of this type of tablets. It was used the Bottenberg et al. method, by the determination of the pH at the surface of one tablet that previously has been soaked in 1 mL of distilled water (pH = 6.5 ± 0.5) for two hours, at room temperature. The pH value was determined by placing the electrode of a CONSORT P601 pH- meter on the surface of the tablet [14];

the swelling degree: represents the capacity of water absorption and it was determined gravimetrically by the introduction of the tablets into a 1.5% agar-agar gel in Petri boxes, incubated at 37ºC ± 1ºC. Each hour, during a six hours interval, each tablet has been taken out from the Petri box and weighted after the gel excess has been removed using filter paper. The swelling degree is expressed according to the equation 4 [15, 16]:

Gs=[(Gt–Gi)/Gi]·100 (4) where: Gs = swelling degree (g); Gt = tablet weight in time t (g); Gi = initial tablet weight (g);

the contact surface of the tablet, expressed as average area of the surface of the tablet, has been calculated according to the equation 5 [9]:

A=2πr(r+ h) (5) where: A = aria of the contact surface (mm2); r = tablet ray (mm); h = tablet height (mm). The data of the equation were obtained under similar conditions with

the ones presented at the determination of the swelling degree, when at every moment the height and the diameter of the tablet have been measured.

The ”ex vivo” evaluation of the buccal bioadhesion time has been performed by adapting the method described by Gupta et al on sheep oral mucosa, obtained two hours after the animal was sacrificed [17]. After the detachement and removal of the basal fat layer and the eventual tissue residue, the membrane was washed with distilled water and then with a buffer solution pH 6.8 at 37°C. Sheep buccal membrane was fixed on a glass slide, every tablet was wetted in the centre with a drop of buffer solution and then placed onto the glass slide by a slight pressing with a wand for 30 seconds. Subsequently, the glass slide was introduced in a cylinder with 200 mL buffer solution pH 6.8 and maintained at 37°C ± 1°C for 2 minutes. Then, to assure the simulation of the oral cavity conditions, a


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palette with 28 rotations/minute speed was activated. The adhesion time is expressed as the necessary time to detach the tablet from the oral mucosa.

Results and discussion The outcomes of the flowing and compressibility properties analysis

of the powders (table I), have shown that the formulation F4, HPC – H based, presented the best flowing properties, each parameter having corresponding values to the excelent type of flow. The flowing characteristics of the formulas based on carbopols were in the accepted limits for each parameter, with the observation that formulas F2 and F3 which contain C 974 and C 934 respectively, presented values of the RH şi IC which recommend the addition of lubricants in the formulations. Also, these formulas did not have a free flowing ”in funnel” (flowing time→ ∞). According to these results, in order to optimize the flowing and compressibility properties, in the formulations F2 and F4 and also in the formulations F5→F8 which contain CHT we introduced 0.5% aerosile and 0.5% magnesium stearate. The formulation F1, C71- based a sort of carbopol directly compressible, fitted in the good flowing type.

Table I Flowing and compressibility parameters F1-F8

Parameter Formula t (g/s) α (º) tg α RH IC (%)

F1 1.68 23.8 0.44 1.22 21

F2 → ∞ 34.4 0.68 1.47 32 F3 → ∞ 41.7 0.89 1.47 32 F4 1.34 21.2 0.38 1.18 17 F5 2.50 27.5 0.52 1.25 20 F6 → ∞ 41 0.87 1.48 32 F7 → ∞ 29.7 0.57 1.42 29 F8 1.89 26.1 0.49 1.35 26

where: t= flowing time (g/s); α – angle of rest (˚); tg α – friction coefficient; RH – Hausner ratio; Ic – Carr index.

The pharmaco-technical properties of the tablets, presented in table

II, have confirmed the data results of the flowing and compressibility parameters analysis by obtaining some values compliant to the specifications of the quality regulations in force: mass uniformity (-2.98/+3.33), friability (0.40 – 0.059%), hardness (43.32 – 53.73 N), diameter (12.04 – 12.10 mm), disintegration time (62.5 – 75 min.).


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Table II The pharmaco-technical characteristics of the 1.5% propiconazole nitrate

biomucoadhesive oral tablets Fo

rmul

a

Mas

s un

iform

ity

(%±)

Har

dnes

s (N

)

Dia

met

er

(mm

)

Thi

ckne

ss

(mm

)

Fria

bilit

y (%

)

Dis

inte

grat

ion

time

(min

utes

)

F1 - 2.25/+2.99 48.46 (1.96)* 12.10 1.65 (0.02) * 0.59 (0.03) * 75 (0.81) *

F2 - 3.31/+2.60 50.80 (2.54)* 12.06 1.57 (0.02) * 0.52 (0.03) * 65 (0.72) *

F3 - 2.75/+3.21 43.32 (1.06)* 12.05 1.72 (0.02) * 0.50 (0.05) * 69 (0.85) *

F4 - 2.89/+3.01 53.73 (1.59)* 12.04 1.60 (0.00) * 0.40 (0.02) * 72 (0.93) *

F5 - 2.98/+3.11 44.76 (1.66)* 12.11 1.61 (0.01) * 0.05 (0.01) * 71 (0.55) *

F6 - 2.51/+3.33 60.86 (1.11)* 12.05 1.69 (0.05) * 0.09 (0.02) * 62.5 (0.69) *

F7 - 2.19/+3.05 61.46 (1.23)* 12.05 1.65 (0.03) * 0.48 (0.01) * 66 (0.65) *

F8 - 2.31/+3.00 48.83 (1.61)* 12.04 1.64 (0.02) * 0.95 (0.04) * 68 (0.73) *

*Standard deviation n = 5 The swelling degree is the parameter with the greatest influence on

the adhesion and drug release properties of the bioadhesive tablets. For formulations F1 and F4, without CTH, the capacity of water absorption decreased as follows: F2>F3>F4>F1. These results can be explained by the different level of crosslinker of the formulated Carbopol sorts, as follows: C 974 (F2) and C 934 (F3) which have a high level of crosslinker, absorbed, from the beginning, a higher water quantity, process mediated by the channels formed between the hydrated polymeric chains, showing the highest swelling degree. Formula 1 (F1), C 974-based, a Carbopol with a reduced level of crosslinker, showed the lowest swelling degree. In this case the polymer influenced the kinetic release of the drug substance, these studies being in progress. The HPC-H from the F4 formed bioadhesive tablets with an intermediary capacity of water absorption, that were characterized by a slower swelling in the first two hours, compared to the formulations F2 and F3. The hydration degree of the formulations F5-F8, CHT-based, was high, especially during the first two hours of the test. Finally, the hydration degree of these formulations was superior to the similar F1-F4 formulations, this phenomenon being determined by the strong hydrophylic and absorbent properties of the CHT (fig. 2).


286

Figure 2

The swelling degree of 1.5% propiconazole nitrate orobiomucoadhesive tablets

The contact surface of the tablet was directly proportional to the swelling degree and the enlargement of the contact surface was mainly determined by the increase of the hight/thickness of the tablet, but there weren't registered any diameter changes (fig. 3).

Figure 3

The enlargement of the contact surface of 1.5% propiconazole nitrate orobiomucoadhesive tablets

The pH of the surface of the tabets is also influenced by the capacity

of water absoption. The formulations F2 and F3 have shown important acidic values due to both an increased water absorption capacity and also to the enhancing of the dissociation phenomenon of propiconazole nitrate (fig.4). Due to the aminic group from the chitosane formulation,


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formulations F5-F8 presented values of the pH that were considerably increased compared to the formulation F1-F4. This phenomenon was predictable and the data results confirmed the necessity of the use in the formulation of an alkaline substance or a buffer in order to create an environment physically close to the oral cavity pH (5.8 – 7.6).

Figure 4

The pH of the orobioadhesive tablets with 1.5% propiconazole nitrate

The results obtained at the ”ex vivo” evaluation of the bioadhesion time have marked out the buccal bioadhesion properties of CTH, the formulations F5-F8 being characterized by increased buccal bioadhesion times (58 – 65.5 minutes). Also, the Carbopol formulations have proven superior buccal bioadhesive properties when compared to formulations based on HPC-H. This result was probably determined consequently to the occurance of some bonds between the ramifications of the polymeric chains from the Carbopol structure and the mucine that is on the mucosa (fig. 5).

Figure 5

The ”ex vivo” time of buccal bioadhesoin of the 1.5% nitrate propiconazole tablets


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Conclusions There were formulated and prepared eight 1.5% propiconazole

nitrate orobiomucoadhesive formulations, based on different hydrophylic polymers in a 20% proportion.

The analysis of the obtained results when the flowing and compressibility characteristics were studied have shown the need of introducing into the formulations F2 and F3, C 974 and C 934- based, as well as into the formulations F5-F8, CTH-based, of some lubricants in order to improve these parameters. For the formulations F1 and F4, the values of the flowing and compressibility parameters corresponded to the excellent flowing type, conclusion also confirmed by the results obtained at the pharmaco-technical analysis, when we obtained, for all studied formulations, values within the limits provided by the regulations in force: mass uniformity, friability, hardness, disintegration time, thickness and diameter.

The results obtained during this study proved the optimal properties of different sorts of Carbopol, with a high level of crosslinker, C 974 and C 934, for the orobiomucoadhesive tablets formulations, prepared by direct compression. Formulations F2, C 71- based and F4, HPC-H-based, although they have a lower swelling degree, showed a satisfactory absorption capacity, which should make us research the influence of the type of polymer on the propiconazole nitrate kinetic release from the orobioadhesive tablets. Depending on the type of polymer from the formulation, the swelling degree and the contact surface decresed as folows: C974 > C934 > HPC-H > C71. The formulations that contain CHT (F5-F8) proved an increased swelling degree during the first 2-3 hours, being characterized, at the same time by superior buccal biomucoadhesive properties compared to the similar formulations, but without CHT (F1-F4). The acid values of the pH from the surface of the tablets recommend the use in the formulation of a buffer in order to assure pH values close to the physiological ones, thus preventing the irritative effect at the application site.

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edition, Taylor & Francisc Group Academic Press, New York, 2005, p. 204 2. SUDHAKAR Y., KOUTSU K., BANDYOPADHYAY A.K., Buccal bioadhesive drug

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5. MARES M., STEFANACHE A., PATRAS X., Antifungal activity of a novel propiconazole derivate, Eur. J. Drug Metabol. Pharmacokinet., 30, 2005, 25.

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Manuscript received: January 20th 2010

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the influence of different polymers on the pharmaco-technological