Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and Sustained Release Solid Dispersions

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1 Research Paper Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 714 International Journal of Pharmaceutical Sciences and Nanotechnology Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and Sustained Release Solid Dispersions Adel M. Aly 1, and Ahmed S. Ali 2 1 College of Pharmacy, King Khalid University, Abha, KSA. 2 College of Pharmacy, Assiut University, Assiut, Egypt. Volume 2 Issue 4 January March 2010 ABSTRACT: Glipizide (GZ) is an oral blood-glucose-lowering drug of the sulfonylurea class characterized by its poor aqueous solubility. Aiming for the production of GZ tablets with rapid onset of action followed by prolonged effect; GZ- Polyethylene glycol (PEG 4000 and 6000) solid dispersions with different ratios, (using melting and solvent evaporation method), as well as, coprecipitate containing GZ with polymethyl-methacrylate (PMMA) were prepared. Four tablet formulations were prepared containing; a) GZ alone, b) GZ: PEG6000, 1:10, c) GZ:PMMA 1:3, and, d)both GZ:PEG6000 1:10 and GZ:PMMA 1:3. The solvent evaporation method showed more enhancement of GZ solubility than the melting one, and this solubilizing effect increased with PEG increment. Generally, PEG6000 showed more enhancement of dissolution than PEG4000 especially at 1:10 drug: polymer ratio (the most enhancing formula). Also, the prepared tablet formulations showed acceptable physical properties according to USP/NF requirements. The dissolution results revealed that tablets containing PEG6000 (1:10) have the most rapid release rate, followed by the formula containing both PEG6000 and PMMA, while that including PMMA alone showed the slowest dissolution rate. Moreover, In-vivo studies for each of the above four formulations, were performed using four mice groups. The most effective formula in decreasing the blood glucose level, through the first 6 hours, was that containing GZ and PEG6000, 1:10. However, formula containing the combination of enhanced and sustained GZ was the most effective in decreasing the blood glucose level through 16 hours. Successful invitro in-vivo correlations could be detected between the percent released and the percent decreasing of blood glucose level after 0.5 hours. KEYWORDS: Glipizide, Polyethylene glycol, Polymethylmethacrylate, Solvent evaporation, Sustained release formulation. Introduction Although there was a great interest in solid dispersion systems during the past four decades to increase dissolution rate and bioavailability of poorly water-soluble drugs, their commercial use has been very limited, primarily because of manufacturing difficulties and stability problems. Solid dispersions of drugs are generally prepared by either melt or solvent evaporation method. Goldberg et al., 1966 (A,B) demonstrated that the entire drug in a solid dispersion might not necessarily be present in a microcrystalline state; a certain matrix, thereby forming a solid solution. In either case, once the solid dispersion was exposed to aqueous media and the carrier dissolved, the drug is released as very fine, colloidal particles. Because greatly enhanced surface area is obtained in this way, the dissolution rate and the bioavailability of poorly water-soluble drugs were expected to be improved. Chiou et.al., 1971 and Ford 1986, reviewed the early research in this area. Serajuddin, 1999 has critically reviewed some of the limitations of solid dispersion. Sustained release, sustained action and prolonged action are terms used to identify drug delivery systems that are designed to achieve a prolong therapeutic effect by continuously release medication and achieve a steady- state blood or tissue level that is therapeutically effective and nontoxic for an extended period of time. In case of orally administered forms; many advantages of sustained release form since the frequency of drug administration is reduced, patient compliance can be improved and drug administration can be made more convenient as well as the total amount of the drug administered can be reduced thus maximizing availability with minimum dose. Glipizide (GZ) is an oral bloodglucose-lowering drug of the sulfonylurea class. Its hypoglycemic activity depends on stimulation of insulin secretion from the beta cells of pancreatic islet tissue. Its solubility has been enhanced by its inclusion inside β- Cyclodextrin (Aly et al., 2003), and, also, by surface solid dispersion through superdisintegrants (Aly et al., 2008). The objective of this investigation was to prepare GZ tablets containing two types of solid dispersion; one containing Polyethyleneglycol (PEG)-GZ for initial enhancing effect and the other were dispersed through 714

2 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 715 Polymethylmethacrilate (PMMA)-GZ matrix as sustaining dose, aiming for producing GZ tablets with rapid onset of action and sustained release properties. Moreover, to carry out in-vivo studies for each of the prepared solid dispersions for their reduction effects on blood glucose level was carried out using four mice groups. Experimental Materials Polyethylene glycol (PEG) 4000and (PEG) 6000 were obtained from Montpelier and Estepansa, Spain. Polymethylmethacrilate (PMMA): medium molecular weight, was from Aldrich Chemical Co., Wisconsin, USA. Aerosil was purchased from Degussa, Belgium. Anhydrous lactose was obtained Janssen chemical, Belgium. Avicel PH 102 was obtained from Janssen chemical, Belgium. Talc was obtained from T.S.S.N.E (Chemicals), Amman, Jordan was used. Methods Preparation of Solid Dispersions Solid dispersion were prepared either by coprecipitation method (solvent evaporation) method or by melting method. In the coprecipitation method, the specified amount of GZ and PEG4000 orpeg6000 (GZ:PEG 1:1, 1:5, 1:10) were dissolved in a least amount of absolute ethanol at room temperature. Alcohol was allowed to evaporate at 35 o C, and the coprecipitate obtained was powdered in a mortar, passed through a 355μm sieve, and stored in a desiccator contains CaCl 2 over night. Solid dispersion matrix formulas containing GZ:PMMA 1:1, 1:2 and 1:3 were prepared using the same above procedures, except that a mixture of ethanol and acetone (1:1) was used as solvent. In the melting method, two types of PEG were utilized, PEG4000 and PEG6000, in different weight ratios (GZ:PEG of 1:1, 1:5, and 1:10). The solid dispersions were prepared by melting the specified amount of PEG in a beaker at 75 C, then adding the specified amount of GZ and allowed to cool to 25 C gradually. The prepared solid dispersions were powdered in a mortar, passed through 355 μm sieve, and stored in a desiccator containing CaCl 2 over night, before study. Characterization of the Prepared Solid Dispersions Differential Scanning calorimetry and X-Ray Diffraction were used in the characterization of the solid dispersion prepared. The methodology for these two is as below: A. Differential Scanning Calorimetry (DSC) Studies: Ten mg of pure GZ powder (A),GZ:PEG 6000,1:1,(B), 1:5,(C), 1:10,(D), and PEG 6000 alone (E), were subjected to Differential Scanning Calorimitry (DSC)DSC studies using Perkin Elmer DSC7 Model. The scanning rate was 10 /min. B. X-Ray Diffraction studies: X-ray diffraction spectra of pure GZ powder (A), GZ:PEG 6000,1:1,(B), 1:5,(C), 1:10,(D), and PEG 6000 alone (E), were recorded using X-ray Diffractometer, Philips 1710, Holland. The scanning rate used was1 o. 2θ/min over the range 0 to 60. Preparation and Evaluation of the Tablets Two types of solid dispersion matrices were selected for tablet preparation: one of best enhanced solubility, GZ:PEG6000 1:10, and the other of most retard release, GZ:PMMA 1:3. Four tablet formulations were prepared as shown in table1. The ingredients of each formula were mixed using cube mixer (Erweka AR 400) for 10 minutes. The mixture was directly compressed into gm flat tablets (8 mm in diameter) using a Korsch, constant rate, tableting machine (EK/O, Germany). After preparation of the tablets, these were evaluated for various common parameters like: Table 1. Composition of Glipizide Tablets. Formula Materials (mg) A B C D Glipizide PEG PMMA Anhyd. Lactose Avicel PH Aerosil Talc A. Uniformity of weight Twenty tablets were taken randomly and weighed individually. The average weight, standard deviation, and coefficient of variation percent C.V% were calculated.

3 716 International Journal of Pharmaceutical Sciences and Nanotechnology Volume 2 Issue 4 January -March 2010 B. Crushing strength The Crushing strength (hardness) of ten tablets selected randomly from each batch was determined using Erweka TBH 30 hardness tester. C. Uniformity of thickness and diameter Twenty tablets taken randomly were tested for thickness and diameter using also, Erweka TBH 30 hardness tester. The standard deviation and the coefficient of variation percent C.V% were calculated. D. Friability The percentage weight loss was determined after rotation of twenty pre-weighed tablets for 4 min at 25 rpm using an Erweka Friabilator TAR 20. E. Disintegration time The time required for the disintegration of one tablet from each batch was determined by using Pharma Test apparatus, Italy. F. Dissolution studies A USP/NF23 Hanson Dissolution Apparatus with six baskets was employed for this purpose. Amount of powder from each formula equivalent to 5mg of GZ was placed in each basket, rotated at 100 rpm in 900 ml of the dissolution medium (Phosphate buffer, ph 7.4) at 37 C. The experiment was run for 2 hours for PEG, and 6 hours for PMMA solid dispersion, during which samples were withdrawn, at suitable time intervals, and replaced by an equal volume of dissolution medium kept at 37 C. Samples were assayed spectrophotometrically at 275 nm for glipizide. Dissolution test for each of the chosen tablet formulations was studied at ph 7.4 (phosphate buffer). One tablet was added to each cub, and the experiment was run as mentioned before for 6 hrs. Each determination was performed in triplicate. In Vivo Studies Four groups of mice were fasted at least 12 hours before the experiment with free water. Each group consists of five mice weighing16-20grams each. Before drug administration, a blood control samples from each mouse of the four groups were taken from behind the eyeball through the angle of ocular cavity using small capillary tubes. The blood glucose level was determined using the glucose-measuring instrument (SURESTEP LIFESCAN, Inc., Johnson- Johnson company, Milpitas, California- USA). The instrument was calibrated just read the result keeping the samples enough dried before reading to avoid any dirt to the lens. The different formulas of glipizide were administered orally to each group of mice using stomach intubation technique. A dose of 1 mg/0.5ml/mouse (that was the effective dose determined in a previous study (Aly, et al, 2003), was administered as a suspension form (freshly prepared). Blood samples were collected where the determination of glucose performed immediately. The sampling time used was at; the first 0.5 hour, then hourly to 12 hours. Results and discussion Coprecipitate Study Two grades of PEG were utilized in this investigation PEG6000 and PEG4000 for the preparation of solid dispersion matrices containing glipizide in 1:1, 1:5 and 1:10 ratio. The adopted techniques were: a) the melting method, and, b) the coprecipitation solvent evaporation method. GZ is poorly soluble in acid medium (0.1N HCl). Thus it was more preferable to study the dissolution in phosphate buffer, at ph 7.4, (according to USP procedure and, also, Hong et al.,1998.generally, PEG6000 showed more enhancing of dissolution rate than PEG4000 especially at 1:10 drug: polymer ratio (the most enhancing formula)(fig 1-5). This may be attributed to the higher molecular weight of PEG6000. Also, coprecipitation method showed more solubilizing effect than the melting method. Generally, the increment of polymer concentration results in more enhancement of solubility of GZ. Sustained Release Solid Dispersion of GZ PMMA in 1:1, 1:2 and 1:3 drug: polymer ratios were used for sustained release study of GZ. The results obtained are illustrated in Fig6. The only sustaining effect could be obtained by 1:3 drug: polymer ratio, whereas 1:1 and 1:2 in contrast, exhibited unexpected rapid release, which may be attributed to the lower of crystallinity resulting in increasing of solubility of GZ. Similar results have been obtained for nitrofurantoin and the same polymer PMMA (Saleh et al.,1993) where enhancing of drug solubility that has been proved by X ray diffraction pattern. However, in 1:3 drug: polymer ratio, the water repellent (hydrophobicity) effect of PMMA retard the release of GZ, while at 1:1 and 1:2 the effect of crystallization was more predominant. X-ray Diffraction Studies In order to clarify physicochemical characteristic of the prepared solid dispersion containing GZ:PEG6000, X-ray diffraction measurements were conducted. Fig. 7 showed the X-ray diffraction patterns of GZ-PEG6000 1:1, 1:5, and 1:10 ratios. The diffraction pattern of GZ containing, PEG revealed the disappearance of many peaks especially at PEG6000 concentration of 5 and 10 ratios were only 2 significant peaks could be observed while many of peaks

4 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 717 have been lowered. This indicates lowering of the drug crystallinity that may result in enhancement of solubility that will be proved by dissolution study. Differential Scanning Calorimitry (DSC) Study For more confirmation of the difference in crystallinity of GZ in coprecipitate, a DSC study was applied. The DSC curves (Fig 8) showed that an endothermic peaks of GZ could be detected at about 210 o C, that have decreased in intensity at 1:1GZ: PEG6000 ratio and disappeared at 1:5 and 1:10 ratio where the peaks of PEG6000 at 60º were predominant reaching comparatively highest intensity at 1:10 ratio where the GZ peak completely disappear indicating decrease in GZ crystallinity. This may explain the best enhancement of GZ dissolution at this concentration. Tablets Study All the prepared tablet formulations showed acceptable physical properties (Table2). The uniformity of weight and diameter fulfill the USP/NF 2002 requirement, as well as, the friability values (from 0.2 to 0.26). The disintegration time values were found to be very rapid in all formulations (less than one min) i.e. acceptable according to the USP/NF 2002 requirements. Fig 9 revealed the dissolution profiles of the prepared tablet formulations. The formula (B) containing GZ:PEG, 1:10 showed the most rapid release followed by the formula (D) including the combination of GZ:PEG,1:10 and GZ:PMMA,1:3, while the formula (C) of GZ:PMMA (1:3), revealed more sustaining effect compared to that containing pure GZ, formula (A). Upon studying the release kinetics of the prepared tablet formulations (Table 3), it could be observed that the release of drug from the prepared tablets, specially those containing sustained release formulations, was according to Higuchi equation i.e. through diffusion with decrease in release rate by time. Table 2. Physical properties of Glipizide tablets selected for in-vivo study. Property Crushing Uniformity Uniformity Uniformity Friability Disintegration Formula Strength of weight of thickness of diameter Value Time (N) (gm) (mm) (mm) (Loss%) (sec.) GZ Free (A) (Control) GZ:PEG(1:10) (B) GZ:PMMA(1:3)(C) GZ:PEG(1:10) & GZ:PMMA(1:3)(D) Table 3. Release kinetics of the prepared tablets. Formula Zero order First order Higuchi A 1 B 2 r 3 A B r A B r Pure GZ,(A) GZ:PEG,1:10, (B) GZ:PMMA,1:3,(C) GZ:PEG,1:10 & GZ:PMMA,1:3, (D) : A is the intercept, 2: B is the slope of line, and 3: r is the correlation coefficient.

5 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 718 In-vivo study Measurement of the in vitro dissolution rate or a related parameter is more likely to offer effective indication of physiologic availability, whereas, dissolution of the drug in vivo is often the rate-limiting factor determining the physiological availability of drug absorption (Banakar, 1983). A powdered GZ was administered in suspension form to the mice. The decrease in glucose level could be observed after 0.5 hours of administration, as showed in Fig10. This effect was gradually enhanced until 12 hours. This observation reflects an increase in the blood level of GZ as a function of the dissolution. Fig10 also, showed the in vivo effect of the prepared three GZ formulations. It could be noticed that, during the first 6 hours; formulations containing GZ:PEG6000 (1:10), formula B, showed comparatively the lowest glucose level, followed by that containing the combination, i.e. formula D (Fig10). However, formulas A and C, which contain free GZ and GZ:PMMA, respectively, showed nearly similar profiles. This may be attributed to the decrease in GZ concentration with formula A but formula C still containing GZ (the sustained formula). During the following ten hours the formula D (combination of enhanced and sustained formula) revealed pronounced sustaining effect followed by that of only PMMA, whereas, the other two formulas showed mild effect on blood glucose level, i.e low GZ level in blood. The t-test (paired t-test) was applied for all the tested formulations for the area under the curve AUC, area above the curve AAC, and the relative availability RA of each formula and the results are shown in Table 4. It could be observed that the most effective formula in decreasing the blood glucose level through 16 hours was that containing the combination of enhanced and sustained GZ formula (i.e. formula D), p <0.05 followed by that of PMMA alone (C), while other two formulas (formula A and B), showed no significant difference compared to the pure GZ formula (as standard). Successful in-vitro in-vivo correlations could be detected between the percent released after 0.5hours and the percent decreasing of blood glucose level after 0.5hours (r 2 =0.9441) (Fig 11). Table 4. In vivo availability results for Glipizide after oral administration of 1 mg to mice through 16 hours. Formula Parameter AUC a AAC b Relative Availability Significance "p"> 0.05 (For AAC data) GZ Free[A] (18.93) c (18.93) (0.0000) ---- GZ:PEG (1:10) [B] (11.38) (11.37) (0.2811) NS GZ:PMMA(1:3)[C] (23.41) (27.21) (0.2439) S GZ:PEG(1:10)&GZ:PM MA(1:3)[D] (11.87) (11.87) (0.1074) S a: AUC means the area under the blood sugar curve. b: AAC means the area above the blood sugar curve. c: Values between parentheses represent the standard error. S: Significant difference. NS: Non-significant difference.

6 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 719 Time min Fig 1. Dissolution profiles of Glipizide from solid dispersion matrix containing PEG6000 by melting method. Fig 2. Dissolution profiles of Glipizide from solid dispersion matrix containing PEG4000 by melting method.

7 720 International Journal of Pharmaceutical Sciences and Nanotechnology Volume 2 Issue 4 January -March 2010 Fig 3. Dissolution profiles of Glipizide from solid dispersion matrix containing PEG6000 by solvent evaporation method. Fig 4. Dissolution profiles of Glipizide from solid dispersion matrix containing PEG4000 by solvent evaporation method.

8 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 721 Fig 5. Dissolution profiles of Glipizide from solid dispersion matrixes containing 1:10 (drug: Polymer ratio) prepared by melting (M) or solvent evaporation (E) method. Fig 6. Dissolution profiles of Glipizide solid dispersion containing PMMA.

9 722 International Journal of Pharmaceutical Sciences and Nanotechnology Volume 2 Issue 4 January -March 2010 A B C

10 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 723 D Fig 7. X-Ray diffraction Pattern of Glipizide (GZ) powder (A), GZ With PEG,1:1,(B), 1:5 (C),and 1:10 (D). Fig 8. Differential Scanning Calorimitry (DSC) of Glipizide (GZ) powder [A], GZ:PEG 6000 (1:1),[B],(1:5),[C], (1:10),[D], and PEG 6000 alone [E].

11 724 International Journal of Pharmaceutical Sciences and Nanotechnology Volume 2 Issue 4 January -March 2010 Fig 9. Release profiles of glipizide from different tablet formulations. Fig 10. Effect of oral administration of 1 mg equivalent of GZ from different formulations blood glucose level of mice (mean of 6 mice).

12 Adel M. Aly, et al. : Preparation and Evaluation of Glipizide Tablets Containing both Enhanced and 725 Fig 11. Correlation between % of GZ released after 0.5h and the % decrease of glucose level after 0.5h for: GZ Free, (A), GZ & PEG, 1:10,(B), GZ & PMMA, 1:3, (C), GZ&PEG 1:10 & PMMA 1:3(D). Conclusions For enhancing glipizide solubility, two methods were utilized (solvent evaporation and melting methods) for preparing solid dispersion containing PEG4000 and 6000.The solvent evaporation method showed more enhancing of solubility than the melting method, specially with PEG6000. Also, coprecipitates containing glipizide with PMMA for sustaining drug release were prepared to produce tablets containing both enhanced and sustained release doses. The prepared tablet formulations showed acceptable physical properties. In-vivo studies for each of the selected four formulations, showed that formula containing the combination of enhanced and sustained GZ was the most effective in decreasing the blood glucose level through 16 hours. Successful in-vitro in-vivo correlations could be detected between the per cent released and the per cent decreasing of blood glucose level after 0.5hours. References Aly, A. M., Kato, M. K. and Othman, M. M. Enhancement of dissolution rate and bioavailability of glipizide through cyclodextrin inclusion complex. Pharmaceutical Technology, 2003, 27(6), Aly A. M. Preparation of Rapidly Disintegrating Glipizide Tablets by Surface Solid Dispersion through Superdisintegrants. International Journal of Pharmaceutical Sciences and Nanotechnology. Volume 1: : Issue October - December Banakar, U. V. and Block, L. H.; Beyond bioavailability testing, Pharm. Tech.,,7, 107,(1983). Chiou, W.L., Riegelman, S. Pharmacautical applications of solid dispersion systems, J. Pharm. Sci. 1971,60, Ford, J. L. The current status of solid dispersions. Pharm. Acta Helv. 1986,61, Goldperg, A. H., Gibaldi, M., Kanig, J. L. increasing dissolution rates and G. I. Absorption of drugs via solid solutions and eutectic mixtures II. Experimental evaluation of eutectic mixture: urea-acetaminophen system. J. Pharm. Sci. 1966,55, (A) Goldberg, A. H., Gibaldi, M., Kanig, J. L. Increasing dissolution rates and G.I. absorption of drugs via solid solution and eutectic mixtures III. Experimental evaluation of griseofulvin-succinic acid solution. J. Pharm. Sci. 1966,55, (B) Hong, S.S., Lee,Y.J., Chung, S.U., and Shim, C.K., J. Controlled release, 51:185 (1998). Saleh, S.I., Ahmed, S.M., Abdel-Rahman, S.I., Khidr., S.H., Aboutaleb. A.E and Aly, A.M. Preparation and release characteristics of some sustained release formulations of nitrofurantoin. S.T.P. Pharma Sciences. 3(5) , (1993). Serajuddin A.T.M. Solid dispersion of poorly water-soluble drugs: Early promises, subsequent problems, and recent breakthroughs. J. Pharm. Sci. 1999,88 (10), ,.