PHARMA SCIENCE MONITOR AN INTERNATIONAL JOURNAL OF PHARMACEUTICAL SCIENCES IN VITRO DISSOLUTION ENHANCEMENT OF ALBENDAZOLE BY PREPARATION OF INCLUSION COMPLEXS WITH HP- ß CYCLODEXTRIN Vipul P. Patel *1, Rajesh K. Parikh 1, Mukesh C. Gohel 1, Tushar R. Desai 2, Dipen R. Bhimani 3, Pravin R. Tirgar 3 1 Department of pharmaceutical technology, L.M. College of pharmacy, Gujarat University, Ahmedabad, Gujarat, India. 2 Department of pharmaceutical technology, R.K. College of Pharmacy, Gujarat technological university, Kasturbadham, Rajkot, Gujarat, India. 3 Department of pharmacology, R.K. College of Pharmacy, Gujarat technological university, Kasturbadham, Rajkot, Gujarat, India. ABSTRACT With the introduction of combinatorial chemistry and high throughput screening, the properties of new chemical entities shifted towards higher molecular weight and increasing lipophilicity that results in decreasing aqueous solubility. It is not surprising that many drug candidates have poor water solubility since the initial selection of drug candidates are based on activity alone. Other physiochemical and biopharmaceutical properties such as permeability, biopharmaceutics and metabolism are rarely considered during the selection process. The aim of this study was to increase dissolution rate of albendazole poorly soluble drugs from BCS class II by complexation process. Complexation was prepared using cyclodextrine. Different techniques were employed for preparation of complexation with cyclodextrin like physical mixture, cogrinding, kneading technology, solvent coevaporation. The physical properties of the prepared solid mass of ABZ was characterized by in vitro dissolution studies, UV-V spectroscopy, Fourior transform infrared spectroscopy, differential scanning calorimetry (DSC) and X- ray powder differaction spectroscopy. Additionaly, phase solubility studies were performed to support the in vitro dissolution study. The results of Fourior transform infrared spectroscopy shows the compatibility of drug with cyclodextrin, while differential scanning calorimetry (DSC) and X-ray powder differaction spectroscopy showed the confirmation of complexation of cyclodextrin with Abz. Key words: Albendazole, BCS class II drugs, complexation, Cyclodextrin Dissolution enhancement, Insoluble drug delivery system www.pharmasm.com 161
INTRODUCTION Albendazole (ABZ), methyl [5-(propyl-thio)-1-H-benzimidazole-2yl] carbamate, is a broad spectrum antihelmintic drug with low aqueous solubility, which may limit its oral absorption [1]. The albendazole therapy is very important in systemic cestode infections specially in inoperable or disseminated cases of hydatidosis [2] and neurocysticercosis [3]. The biggest problem of albendazole is its low and erratic availability as a result of its low aqueous solubility. One possible way of overcoming this problem is to alter the physical properties of the drug by forming a complexation with hydroxy propyl beta cyclodextrin [4]. Cyclodextrins (CDs) are a group of structurally related cyclic oligosaccharides that are formed by enzymatic cyclization of starch. The three most common naturally occurring CDs are a-cyclodextrin (acd), b-cyclodextrin (bcd) and g-cyclodextrin (gcd) consisting of six, seven and eight (a-1,4)-linked a-d-glucopyranose units, respectively. The CD molecules are cone-shaped with a somewhat hydrophobic central cavity and hydrophilic outer surface. They are capable of forming inclusion complexes with many drugs by taking up a whole drug molecule, or more frequently, some hydrophobic part of it, into the cavity [5]. MATERIALS AND METHODS ABZ were kindly supplied by Pramukh pharmaceutical pvt. ltd. (Gujarat, India), HPbCD was supplied by Mepro Pharmaceutical pvt. Ltd (Gujarat, India). All the products and materials used in this study comply with the pharmaceutical and analytical standards, respectively. All the research work was carried out at L.M. College of Pharmacy, Ahmedabad during year 2008-2009. Phase solubility study [6] : Phase solubility study for ABZ was performed as described by Higuchi and Connors. Excess amount of ABZ was added into 100 ml 0.1 N HCL containing carrier at various concentrations and shaken for 96 h at room temp on a shaker (time period of 96 hr was previously determined for achievement of albendazole equilibilium). After equilibilium, the suspensions were filtered through 0.45 μm Millipore membrane. filters. The first 15% of the filtrate was discarded to avoid any potential loss of the drug, because www.pharmasm.com 162
of absorption by the filter until and the subsequent filtrate was collected. The filtrate was appropriately diluted by methanol and the concentration of the albendazole in the filtrate was determined by UV spectrophotometer (UV-1601PC, Shimadzu) at 291 nm. Earlier experiments showed that the presence of different carrier did not interfere with the assay at the concentration employed. Solubility measurements were performed in triplicate. Methods of preparation [7] : Preparation of physical mixture (PM): The physical mixture of ABZ with hydroxy propyl β cyclodextrin was prepared in 1:1.5, 1:2 and 1.5 geomatrix ratio by means of spatula for 20 minutes and passed through 80 mesh screen. Preparation of cogrinding product (CG): For co-grinding product, ABZ with hydroxy propyl β cyclodextrin were mixed and triturated in glass mortar pestle for 20 minutes and passed through 80 mesh screen. Preparation of kneaded product (KN): The kneaded product was prepared by addition of drug into the paste of cyclodextrin, and triturating the resultant mixture till cracking sound appear. The resultant mass was dried at room temp. and pass through 80 mesh screen. Preparation of co-evaporated product (CE): For the preparation of co-evaporated product, an aqueous solution of cyclodextrin was added to a methanolic solution of albendazole. The resulting mixture was stirred for 1 hour and evaporated at 45-50 c until nearly dry. The resulting mass was allowed to dry at room temp for two consecutive days. These dried mass pulverized and pass through 80 mesh screen. Characterization UV Spectroscopy: UV spectra were obtained on a UV spectrophotometer, Shimadzu (L.M. College of pharmacy, Ahmedabad) with a wavelength range of 200 nm- 400 nm. Fourier transform infrared (FTIR): Fourier transform infrared (FTIR) spectra were obtained on a spectrophotometer (L.M. college of pharmacy, Ahmedabad) with a resolution of 2 cm -1 from 3500 to 600 cm -1. Pellets were prepared by gently mixing the sample with potassium bromide (1:100 ratio). Differential scanning calorimetry (DSC): DSC measurements were made on a Pyriscalorimeter (Perkin-Elmer). Approximately 3 5 mg samples were accurately weighed into standard aluminum pans. An empty pan was used as reference. The samples were www.pharmasm.com 163
heated from room temperature to 290 C with scan rates 5 C/min. All DSC curves were normalized to a sample mass of 1 g. The instrument was calibrated using indium (melting point, 156.61 C; enthalpy of fusion, 28.71 J, g 1). X Ray diffraction: The physical state of albendazole in pure drug powder and in optimized mass was evaluated by powder X-ray diffraction. Powder X-ray diffraction (XRD) patterns were determined with an X-ray diffractometer (SICART Mota bazaar, Vallabh Vidyanagar), employing Ni-filtered CuK α radiation source operating at 30 kvoltage and a current of 40 ma. In vitro dissolution characterization: In vitro dissolution studies were carried out in 900 ml of 0.1 N hydrochloric acid containning 0.05 % w/v SLS using USP dissolution apparatus with an aggitation of 100 RPM. SLS was used to maintain sink condition. Powder sample equivalent to 200 mg of drug was filled in empty capsule shell and immersed in the dissolution medium. The dissolution sample (10 ml) withdrawn at different time intervals was filtered through a membrane filter (0.45 µm). This filtered sample was diluted sufficiently by 0.1 N HCL and assayed spectrophotometrically at 291 nm. The cumulative percentage of drug release after 15 min, 30 min, 45 min, 60 min, 90 min, 120 min, 150 min, 180 min, 210 min and 240 min is measured. TABLE 1: Formulation batches for Abz- Hydroxy propyl beta cyclodextrin complexation Methods of preparation Drug to polymer ratio Batch code Physical Mixture Cogrinding product Kneaded product Co-evaporated product 1:1.5 B1 1:2 B2 1:2.5 B3 1:1.5 B4 1:2 B5 1:2.5 B6 1:1.5 B7 1:2 B8 1:2.5 B9 1:1.5 B10 1:2 B11 1:2.5 B12 www.pharmasm.com 164
RESULTS AND DISCUSSION Phase solubility study: Figure 1 Phase solubility study of Abz with Hydroxy propyl Beta cyclodextrin Above figure shows that solubility profiles of ABZ in 0.1 N HCL influenced by carrier material concentration at room temp. The solubility curve with correlation coefficient squared values (r2) >0.95 (r2=0.95) was regarded as a straight line (AL type) (Higuchi and Connors, 1965). UV Spectroscopy: Formulation excipients selected on the basis of preliminary tests, which demonstrates no interference of these excipients with the λ max of ABZ. The complex formation with cyclodextrin alters the original UV absorption spectrum of the molecule usually bathochromic shift and or band broadening occurs. The shift of the UV absorption maxima upon complex formation may be explained by a particular shielding of the excitable electrons in the CD cavity [8]. Figure 2 Photographic image showing λ max of albendazole www.pharmasm.com 165
Figure 3 Photographic image showing λ max of albendazole after complexation FTIR The spectrum for ABZ showed N-H stretching vibration at 3323 cm -1, bending vibration at 1525-1630 cm -1 and aliphatic C-H at 2958 cm -1. The spectrum for ABZ has NH stretching vibration at 3323 cm -1 due to carbamate-nh. PM of ABZ showed superimposed spectra of ABZ and hydroxy propyl beta cyclodextrin which proves the compatibility of excipients with the ABZ. Reduction in intensity of transmittance occurred also for NH bending vibrations of ABZ (1525-1630 cm -1 ) in our optimized batch containing solid binary system. From these results, it can be speculated that drugcarrier hydrogen bonding existed in these solid binary system, causing reduced drug recrystallization [9]. Figure 4 Fourier transforms infrared spectroscopy of Albendazole www.pharmasm.com 166
Figure5 Fourier transform infrared spectroscopy of PM Figure 6 Fourier transforms infrared spectroscopy of kneaded product albendazole Differential scanning calorimetry (DSC): The DSC thermograms of albendazole, albendazole (PM), and the inclusion complexes of albendazole are illustrated into the Figure. Physical mixture showing almost similar identical melting endotherm and spectra are overlapable which proves the compatibility of used excipients. The complex formation was suggested by a decrease in enthalpy of dehydration/desolvation when compared to the PM. The DSC curve of albendazole shows a sharp melting endotherm at www.pharmasm.com 167
198 C. The melting endotherms into the prepared complexes are of decreased intensity with lowering of melting temp. and more flattened compared with that in the pure drug, probably due to greater disorder in the crystal structure. Figure 7 DSC curve of albendazole Figure 8 DSC curve of albendazole PM www.pharmasm.com 168
Figure 9 DSC curve of albendazole kneaded product X Ray diffraction The Albendazole presented in a crystalline form as demonstrated by various intense diffraction peaks in the figure. The crystalline peaks located at 7.01º, 11.22º, 13.83º, 17.87º, 19.50º, 20.71º, 22.10º, 27.10º, and 28.16º (2 θ) corresponding to albendazole crystals were observed. Albendazole had a more intense peak at 7.01º, 11.22º, 17.87º, 19.50º, 20.71º, 22.10º, 27.10º, and 28.16º in addition to relatively less intense peaks at 13.83º, 54.01º. XRD patterns of kneaded systems showed reduced diffraction intensity as indicated in Fig 10 and 11. Figure 10 XRD patterns of pure albendazole www.pharmasm.com 169
Figure 11 XRD patterns of inclusion complex of albendazole TABLE 2: In vitro dissolution profiles of albendazole from batch B1-B6 Time B0 B1 B2 B3 B4 B5 B6 (Minutes) DP 15 6.2 8.1 9.6 11.1 9.3 10.1 13.4 DP 30 8.9 11.0 13.4 17.5 12.4 14.2 19.2 DP 45 10.2 13.6 15.2 19.3 15.9 17.8 21.4 DP 60 11.8 16.8 18.5 21.7 18.4 20.5 23.6 DP 90 13.6 18.1 22.3 25.3 19.7 23.8 24.9 DP 120 15.2 19.7 23.5 27.2 20.9 26.2 26.9 DP 150 19.4 24.3 25.6 28.5 24.8 28.4 29.7 DP 180 22.8 26.7 28.2 30.8 28.3 31.4 33.1 DP 210 25.3 30.5 31.6 32.4 30.5 35.9 36.8 DP 240 28.5 33.9 35.7 37.1 35.2 37.6 39.8 www.pharmasm.com 170
TABLE 3: In vitro dissolution profiles of albendazole from batch B7-B12 Time (Minutes) B7 B8 B9 B10 B11 B12 DP 15 13.6 19.58 23.8 12.2 19.4 22.0 DP 30 19.2 25.29 29.8 19.8 25.8 30.7 DP 45 24.5 30.77 33.6 25.2 31.2 35.6 DP 60 29.6 36.20 39.3 30.1 36.5 39.8 DP 90 33.6 40.09 44.6 34.1 41.7 45.0 DP 120 35.9 45.11 48.3 36.0 46.3 50.2 DP 150 38.6 49.39 51.7 38.4 49.4 50.9 DP 180 41.5 54.11 55.8 41.9 55.4 56.2 DP 210 45.2 58.28 60.0 46.5 58.6 59.4 DP 240 48.6 62.69 63.4 49.7 63.1 64.2 Figure 12 Comparative dissolution profile of batch B1- B6 www.pharmasm.com 171
Figure 13 Comparative dissolution profiles of batch B7-B12 CONCLUSION The aim of this work was to improve the dissolution rate of albendazole which is required for improving the dosage form characteristic and also to reduce fluctuation in dissolution profile as well as for better invivo characterization. Many techniques are known to improve dissolution rate of poorly soluble drugs amongst these preparation of physical mixture, co-grinding techniques, kneading techniques and solvent co-evaporated techniques are selected in this research work because of its ease of preparation, ease of optimization, and reproducibility. Amongst these techniques kneading method and solvent co-evaporated methods found to be more effective than previous two techniques.. In case of albendazole as alone hydroxy propyl beta cyclodextrin cannot produce satisfactory enhancement in dissolution rate and also due to limits of using polymer concentration, third polymer as an acid solubilizer may added which increase the binding property of ABZ with hydroxy propyl beta cyclodextrin and may be helpful for improving further dissolution rate. ACKNOWLEDGEMENTS This work was entirely dedicated to my research guide Dr. M.C. Gohel and Dr R.K. Parikh for their valuable cooperation and suggestion in my research work. www.pharmasm.com 172
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