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Improvement of water solubility and in vitro dissolution rate of gliclazide by complexation with β-cyclodextrin1
Pharmaceutica Acta Helvetiae 74 Ž2000. 365–370 www.elsevier.comrlocaterpharmactahelv
Improvement of water solubility and in vitro dissolution rate of gliclazide by complexation with b-cyclodextrin 1 a a ¨ ˙ Yalc¸ in Ozkan , Tamer Atay a , Necati Dikmen , As¸kin Is¸imer a , Hassan Y. Aboul-Enein b,) b
a Department of Pharmaceutical Technology, Gulhane Military Medical Academy, 06018, Etlik-Ankara, Turkey ¨ Bioanalytical and Drug DeÕelopment Laboratory, Biological and Medical Research Department (MBC-03), King Faisal Specialist Hospital and Research, PO Box 3354, Riyadh 11211, Saudi Arabia
Received 8 September 1999; received in revised form 15 October 1999; accepted 31 October 1999
Abstract Inclusion complexes of gliclazide with b-cyclodextrin were prepared using different two methods: neutralization and recrysstalization. Host–guest interactions were studied in the solid state by X-ray diffractometry and infrared spectroscopy. The stability constant between gliclazide and b-cyclodextrin was calculated from the phase solubility diagram. It was found that the neutralization technique and a solid complex of gliclazide with b-cyclodextrin in a molar ratio of 1.5:1 could be used to prepare the amorphous state of drug inclusion complexes. The dissolution rates of gliclazide from the inclusion complex made by neutralization was much faster than the pure drug, physical mixture of drug and cyclodextrin, recyristalization system and also comparable to the data reported in literature. Results of this report indicate that b-cyclodextrin could be useful for the solid gliclazide formulations as it may results in a more rapid and uniform release of the drug. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Cyclodextrin; Gliclazide; Dissolution rate; Neutralization; Recrysstalization; Solubility
1. Introduction Cyclodextrins ŽCD. are enzymatically modified starches made up of glucopyranose units. Three different CDs are known. The a-CD consist of six glucopyranose units, b-CD of seven units and g-CD of eight units. All of the CDs are crystalline and nonhygroscopic and they feature a cylinder-shaped, macro ring structure with a large internal axial cavity. The outer surface of a CD molecule is hydrophilic but internal cavity is apolar ŽSaenger, 1980; Szejli, 1988; USP, 1995.. The CDs comprise a family of cyclic oligosaccharides knwon to form noncovalent inclusion complexes with many substances specially with hydrophobic drug molecules. Inclusion complexation of drugs with CDs may be useful to solve various pharmaceutical
) Corresponding author. Tel.: q966-1-442-7859; fax: q966-1-4427858. E-mail address: [email protected] ŽH.Y. Aboul-Enein.. 1 Presented at the 2nd International Meeting on Pharmacy and Pharmaceutical Sciences, September 1998, Istanbul, Turkey.
formulation problems such as imrovement of stability ŽAndersen and Bundgaard, 1984., solubility, dissolution rate ŽPitha et al., 1986; Blanco et al., 1991; Ammar et al., 1999. and bioavailability ŽChow and Karara, 1986; Bekers et al., 1991.. Gliclazide w1-Ž3-Azabicyclo Ž3,3,0.oct-3yl.-3-p-tolylsulphonylureax is a second generation of hypoglycemic sulfonylureas ŽReynolds, 1993.. The major drawback in the therapeutic application and efficacy of gliclazide as oral dosage forms is its very low aqueous solubility because of its hydrophobic nature. It is characterized by low dissolution rate in water. For these reasons, its bioavailability shows interindividual variations as shown by Gillmann et al. Ž1990.. The present study was carried out to investigate the inclusion mode between gliclazide and b-CD in the solid state using X-ray diffractometry ŽXRD. and infrared spectroscopy ŽIR.. Neutralization, recrysstalization and physical mixing were employed for the preparation of gliclazide systems with b-CD and the effect of complexation in the solubility and dissolution rate of gliclazide was evaluated. To date, the solid state characterization and dissolution
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characteristics of gliclazide-b-CD, inclusion complexes have not yet been reported, except in recent works of Moyano et al. Ž1997a,b.. The primary objective of the present study is to investigate the possibility of improving the release properties of gliclazide via complexation with b-CD. Furthermore, the dissolution rate profile and the inclusion complex molar ratio of gliclazide-b-CD system in aqueous media are reported. The investigation suggests that a b-CD complex of gliclazide may be sufficiently soluble to be clinically useful.
2. Experimental 2.1. Materials Gliclazide was a gift from Servier ŽIstanbul, Turkey. and a , b and g-CDs were supplied by Chinoin Pharmaceutical and Chemical Works ŽHungary.. All other chemicals were of analytical grade and supplied by Sigma ŽSt. Louis, MO. or Merck ŽDarmstadt, Germany.. 2.2. Phase-solubility assays The phase-solubility studies for gliclazide were tested with a , b and g-CDs. According to the obtained results, the best solubility of gliclazide was obtained with b-CD. Ten milligrams of gliclazide were accurately weighed into each of 10 ml screw-capped vials to which 10 ml of aqueous solutions containing various concentrations of CD’s Ž0.001–0.01 M. were added. The sealed flasks were shaken at a controlled room temperature of 25 " 0.58C. After equilibration up to 72 h, an aliquot was filtered with a 0.2 mm membrane filter. Aliquot portions of the filtrate were properly diluted and analyzed by UV spectrophotometry at 227 nm. 2.3. Preparation of solid complex The solid complexes of gliclazide with b-CD 1:1, 1:2, 1.5:1 Žmolar ratio. were prepared using neutralization and coprecipitation methods. 2.3.1. Neutralization method One gram gliclazide was accurately weighed and dissolved in 50 ml, 1 N sodium hydroxide solution, followed by 2.33 g b-CD. This mixture was placed on a magnetic stirrer and stirred until a clear solution was obtained. Fifty millilitres 1 N hydrochloric acid was added drop by drop, and the solution was stirred for 2 h with magnetic stirrer. The formed precipitate was separated by vacuum filtration and washed repeatedly and dried at room temperature. 2.3.2. Recrysstalization method Gliclazide was first prepared by adding 1 g of gliclazide to 50 ml of methylene chloride. To this solution 2.33 g of
accurately weighed b-CD was added. This mixture was stirred until a clear solution Žabout 2 h. was obtained. This mixture was placed in a vacuum and the solvent was allowed to evaporate at 408C ŽSaenger, 1980; Seo et al., 1983.. 2.3.3. Preparation of the physical mixtures Physical mixtures of gliclazide with b-CD Ž1:1, 1:2, 1.5:1 molar ratio. were prepared by simple blending in a ceramic morter. 2.3.4. Characterization of the mixtures and the inclusion complexes XRD was carried out using a Philips PW 1730 X-ray generator ŽHolland.. The operation conditions were as follows: X-ray source; Ni-filtered; Cu K a radiation; voltage 40 kV; current 20 mA; time constant 2 s; scanning rate 28 cmy1 . IR was carried out using a Shimadzu IR-470 ŽJapan. model infrared spectrophotometer, according to the KBr disk method. 2.3.5. Dissolution rate studies In vitro dissolution studies of pure drug, physical mixtures and inclusion complexes prepared by the two methods of all complex ratios were evaluated. Dissolution studies for the samples prepared by neutralization and recrystallization method were carried out according to the USP XXIII Ž1995. paddle method ŽCaleva Model 7ST, England.ŽUSP Apparatus 2.. Powder samples containing 10 mg of gliclazide or its equivalent amount of inclusion complexes or physical mixture form were placed in 100 ml of the dissolution medium in a cell at 37 " 0.58C for 12 min. In this assay, 900 ml of dissolution fluid Ž0.1 N HCl, pH 1.2. and stirring rate at 100 rpm were used. At predetermined time intervals, samples were automatically taken for spectrophotometric determination of gliclazide concentration following automatically filtration at 227 nm. All samples were analysed in triplicate. Dissolution efficiencies after 120 min were calculated according to five different kinetics such as, zero-order, first-order, HixsonCrowell, RRSBW and Q y 6t.
3. Results and discussion 3.1. Phase-solubility studies Table 1 shows the effects of 3 CD polymers on the solubility of gliclazide increased in the order of b-CD ) a-CD ) g-CD. The cavity size in the polymer of b-CD seems to be optimum to entrap the gliclazide molecule and consequently provides the greatest solubilization effect. Solubility measurements were carried out according to the method described by Higuchi and Connors Ž1965.. The phase solubility profiles for the complex formation be-
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Table 1 Phase-solubility results of gliclazide in various cyclodextrins Medium
Solubility mgrl
Confidence limits 95%
Relative standard deviation
0.01 M a-cyclodextrin 0.01 M b-cyclodextrin 0.01 M g-cyclodextrin
32.48 35.50 29.13
"0.32 "0.24 "0.48
0.397 0.268 0.669
tween gliclazide and b-CD are presented in Fig. 1. Inclusion complex showed a typical Bs-type solubility curve ŽHiguchi and Connors, 1965., where the initial ascending portion is followed by a plateau region and then a decrease in total gliclazide solubility accompanied by precipitation of a microcrystalline complex. Stability constant of this inclusion complexation was found to be 195 My1 to make use of the stoichiometric calculation for improvement of Bs-type solubility curve. Although the geometrics within the inclusion complexes in aqueous solutions can not be accurately defined, it is reasonable to assume a 1.5:1 M complexation, because this would allow maximum contact of hydrophobic portion of the organic substrate with the apolar cavity of b-CD ŽGriffiths and Bender, 1973.. 3.2. EÕidence of complex formation in solid state To confirm the complexation of gliclazide with b-CD in the solid state, XRD and IR were employed and compared with the corresponding physical mixtures in the same molar ratio. The X-ray diffractograms of gliclazide, b-CD and its binary complexes in comparison with the physical mixtures are shown in Fig. 2. The diffraction pattern for the physical mixture closely resembles that of b-CD, as expected. However, the pattern for the complex differs significantly from that of the physical mixture. Some peaks disappeared, some peaks appeared and some
Fig. 1. Phase solubility diagram of Gliclazide-bCD inclusion complex at room temperature.
Fig. 2. X-ray diffraction patterns of: ŽA. Gliclazide, ŽB. b-CD ŽC., Physical mixture of Gliclazide, and b-CD ŽD. Gliclazide– bCD inclusion complexes by recrystallization method Ž1.5:1., ŽE. Gliclazide– bCD inclusion complexes by neutralization method Ž1.5:1..
peaks height are decreased. The appearance of new peak was observed, indicating the presence of new solid crystalline phases, corresponding to inclusion complexes of the same nature. The functional groups of gliclazide involved in the complexation were also involved in IR. Infrared spectra of the gliclazide and inclusion complexes by recrystallization and neutralization method and physical mixture of gliclazide with b-CD are shown in Fig. 3. Infrared spectrum of gliclazide is characterized by the absorption of the carbonyl ŽC-O. sulphonylurea group at 1706 cmy1 . In the spectra of the inclusion complex, this band was shifted towards higher frequencies at 1725 cmy1 . Also, the NH group which is located at 3265 cmy1 from the IR spectrum of gliclazide was shifted to 3365 cmy1 . The sulphonyl group bands ŽS-O. are located at 1349 cmy1 and 1162 cmy1 in pure gliclazide. In the conclusion complex, the asymmetrically vibration peak of S-O band
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groups are shifted towards higher frequencies, suggesting that after the formation of the inclusion complex existing bonds were broken and also reduced in their intensities. Thus, as spectral changes always concern C–OH, –CH 2 and CH groups of the b-CD, it should be suggested that the host–guest interactions are dominated by hydrogen bonds among the above mentioned groups. 3.3. Dissolution behaÕiour of complexes Fig. 4 shows the dissolution behaviour of gliclazide alone, from inclusion complexes and physical mixtures. The release rate profiles were drawn as the percentage gliclazide dissolved from the inclusion complexes, physical mixture and pure drug versus time. It is evident that both the complexes and physical mixtures exhibit a faster dissolution rate than the free drug. The remarkable increase was for the inclusion complex prepared by the neutralization method rather than the recrystallization method. The amounts of gliclazide dissolved after 5, 10, 25 and 60 min are presented in Table 2. According to the obtained results the inclusion complex prepared by the neutralization method and ratio of the complex 1.5:1 dissolved in 5 min. The drug dissolved very rapidly within the first five minutes and by the end of 10 min 99.25% of drug was dissolved in the gastric medium. The extent of the enhancement of the dissolution rate was found to be dependent on the preparation method, since the neutralization method exhibits the highest dissolution rates all complexation ratios of gliclazide and b-CD. This behaviour may be attributed to the high energetic amorphous state and inclusion complex formation. The small dissolution rate increase found for the physical mixture is only due to the wetting effect of the b-CD. Fig. 3. IR spectra of: ŽA. Gliclazide, ŽB. b-CD ŽC., Physical mixture of Gliclazide and b-CD, ŽD. Gliclazide– bCD inclusion complexes by recrystallization method Ž1.5:1., ŽE. Gliclazide– bCD inclusion complexes by neutralization method Ž1.5:1..
was obtained at between 1394–1342 cmy1 as three decreased intensity peaks. Symmetrically vibration peak of S-O band which is located at 1162 cmy1 was shifted to 1155 cmy1 in pure gliclazide. The IR spectrum of b-CD is characterized by intense bands at 3300–3500 cmy1 , associated with the absorption of the hydrogen bonded-OH groups of b-CD. The vibration of the –CH and –CH 2 groups appear in the 2800–3000 cmy1 region. The observed changes in the infra red spectra of the binary systems may be explained by the different preparation methods. As can be seen in the spectral pattern of the physical mixtures, it corresponds simply to the superposition of the IR spectra of the two components. However, in the neutralization and recrystallization procedures almost total smoothing of the band situated at 3200–3700 cmy1 was observed. Moreover, the vibrations of sulphonylurea
Fig. 4. Dissolution rate profiles of Gliclazide and its b-CD system in 0.1 N HCl at 378C. Žl. Gliclazide Ž'. Physical mixture Ž1.5:1. Žv . Gliclazide b-CD complex by recrystallization method Ž1.5:1. ŽB. Gliclazide b-CD complex by neutralization method Ž1.5:1. Each point: mean" S.D.
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Table 2 Mean percentages of gliclazide dissolved from 1.5:1 molar ratio of inclusion complexes, physical mixture and pure drug after different time intervals in pH 1.2 at 37"0.58C Preparation method
Released percentage of gliclazide"S.D.
Pure gliclazide Physical mixture Recrystallization Neutralization
5 min
10 min
25 min
60 min
10.00"2.77 40.17"1.36 61.55"2.45 97.85"2.40
18.67"1.34 48.36"0.99 69.13"1.46 99.25"1.94
41.16"0.88 61.19"3.76 79.18"1.86 99.87"3.02
47.19"1.34 70.05"4.24 80.29"1.27 100.0"2.35
Five different kinetics such as, zero-order, first-order, Hixson–Crowell, RRSBW, Q y 6t were applied to the results obtained from the dissolution studies of inclusion complexes, physical mixtures and pure drug. The results were evaluated kinetically ŽHiguchi, 1963; Langenbucher, 1976. ŽTable 3.. According to the investigation of the kinetic assessment of the release data, the best released kinetic was found to be RRSBW for all formulations, because of the highest correlation coefficient, lowest AKAIKE’s information criteria and also lowest sum of weighted squared deviations. For RRSBW kinetic, T63.2% , results were obtained 1 min for inclusion complexes; 33.61
min for physical mixture and; 132.43 min for pure gliclazide. According to this kinetic, low b value corresponds with a steeper initial slope followed by a flattened tail in the final part. Actual curves tend to have shape parameters between 0.5 and 2. When no disintegration occurs at all or disintegration is extremely fast, the rate of dissolution will decrease monotonously and the cumulative curve will also be monotonous with b F 1. In this study, shape factor Ž b . obtained from RRSBW was found to be - 1 for all formulations. The release of the drug from inclusion complexes is nearly completed within 10 min for neutralization method.
Table 3 The kinetic assessment of dissolution data kr 0 : Zero-order release rate constant. kr: First-order release rate constant. T : Value stands for the time for 63.2% release of the drug. b : Shape factor. k: Rate constant obtained from Qy6t kinetic. K : Rate constant obtained from Hixson–Crowell kinetic. r 2 : Determination coefficient. AIC: AKAIKE’s information criteria. SWSD: Sum of weighted squared deviations. Applied kinetics
RRSBW
Zero-order
First-order
Hixson–Crowell
Qy6t
Formulations
T63.2% b r2 SWSD AIC kr 0 r2 SWSD AIC kr r2 SWSD AIC K r2 SWSD AIC k r2 SWSD AIC
Gliclazide
Physical mixture Ž1.5:1.
Neutralization method Ž1.5:1.
Recrystallization method Ž1.5:1.
132.43 0.57 0.846 0.055 y23.72 1.77 0.664 0.43 y3.954 0.281 0.737 0.41 y6.53 0.193 0.713 0.258 y10.92 33.47 0.796 0.089 y21.67
33.61 0.328 0.988 0.0038 y48.78 1.648 0.811 0.149 5.65 0.456 0.899 0.137 2.66 0.341 0.871 0.896 y1.67 81.45 0.917 0.480 y9.53
1 0.632 0.914 0.041 y46.71 0.066 0.407 0.41 14.37 9.57 0.855 0.725 9.72 0.966 0.778 0.268 6.28 184.07 0.546 1.55 5.596
1 0.112 0.842 0.033 y33.33 0.708 0.506 3.307 12.35 0.284 0.585 3.32 10.30 0.417 0.558 2.05 4.34 113.22 0.654 y3.94 y0.914
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4. Conclusion The best solid inclusion complexes of gliclazide with b-CD can be obtained by the neutralization method using molar ratio 1.5:1. According to our results from the dissolution rate studies, inclusion complexes prepared by neutralization method exhibits better and faster solubility and dissolution rate profile compared to the reported literature method ŽPitha et al., 1986.. These results are probably due to Ža. the difference in preparation methods, Žb. using b-CD from various manufacturers, and Žc. using different molar ratio for the preparation of the inclusion complexes. The inclusion complexes of b-CD-gliclazide prepared by the neutralization method offers an improvement in the solid pharmaceutical formulations of the drug, which renders it sufficiently soluble for its clinical application.
References Ammar, H.O., Ghorab, M., El-Nahhas, S.A., Emara, L.H., Makram, T.S., 1999. Inclusion complexation of furosemide in cyclodextrins. Pharmazie 54, 142–144. Andersen, F.A., Bundgaard, H., 1984. Inclusion complexation of metronidazole benzoate with b-cyclodextrin and its depression of anhydratehydrate transition in aqueous suspensions. Int. J. Pharm. 19, 189–197. Bekers, O., Uijtendaal, E.V., Beijnen, J.H., Bult, A., Underberg, W.J.M., 1991. Cyclodextrins in pharmaceutical field. Drug Dev. Ind. Pharm. 17, 1503–1549. Blanco, J., Vila-Jato, J.L., Otero, F., Anguiano, S., 1991. Influence of method of preparation on inclusion complexes of naproxen with different cyclodextrins. Drug Dev. Ind. Pharm. 17, 943–945.
Chow, D., Karara, A., 1986. Characterization, dissolution and bioavailability in rats of ibuprofen-b-cyclodextrin complex system. Int. J. Pharm. 28, 95–101. Gillmann, A.G., Rall, T.W., Nies, A.S., Taylor, P., 1990. In: Goodman and Gillmann’s The Pharmacological Basis Therapeutics. 8th edn. Pergamon, Maxwell House, New York, USA, pp. 1485–1486. Griffiths, D.W., Bender, M.L., 1973. Cycloamyloses as catalysts. Adv. Catal. 23, 209–261. Higuchi, T., 1963. Mechanism of sustained action medication. J. Pharm. Sci. 52, 1145–1149. Higuchi, T., Connors, K.A., 1965. Phase-solubility techniques. Adv. Anal. Chem. Instrum. 4, 117–212. Langenbucher, F., 1976. Parametric representation of dissolution rate curves by the RRSBW distrubution. Pharm. Ind. 38, 472–477. Moyano, J.R., Arias-Blanco, M.J., Gines, J.M., Giordano, F., 1997a. Solid-state characterization and dissolution characteristics of gliclazide-b-cyclodextrin inclusion complexes. Int. J. Pharm. 148, 211–217. Moyano, J.R., Arias-Blanco, M.J., Gines, J.M., Rabasco, A.M., PerezMartinez, J.I., Mor, M., Giordano, F., 1997b. Nuclear magnetic resonance investigations of the inclusion complexation of gliclazide with -b-cyclodextrin. J. Pharm. Sci. 86, 72–75. Pitha, J., Milecki, J., Fales, H., Pannell, L., Uekama, K., 1986. Hydroxypropyl-b-cyclodextrin: preparation and characterization; effects on solubility of drugs. Int. J. Pharm. 29, 73–82. Reynolds, J.E.F. ŽEd.., Martindale. The Extra Pharmacopoeia. 30th edn. The Pharmaceutical Press, London, pp. 279–280. Saenger, W., 1980. Cyclodextrin inclusion compounds in research and laboratory. Angew. Chem. Int. Ed. Engl. 19, 344–362. Seo, H., Tsruoka, M., Hashimato, T., Fujinaga, T., Otagiri, M., Uekama, K., 1983. Enhancement of oral bioavailability of spiranolactone by beta and gamma-cyclodextrin complexations. Chem. Pharm. Bull. 31, 286–291. Szejli, J. ŽEd.., Cyclodextrin Technology. Kluwer Academic Publishers, Dordrecht, pp. 1–78. The United States Pharmacopeia, 995. 23rd Revision, Rand Mc Nally, Tounton, MA, pp. 1791–1792, pp. 2220–2221.
Improvement of water solubility and in vitro dissolution rate of gliclazide by complexation with b-cyclodextrin 1 a a ¨ ˙ Yalc¸ in Ozkan , Tamer Atay a , Necati Dikmen , As¸kin Is¸imer a , Hassan Y. Aboul-Enein b,) b
a Department of Pharmaceutical Technology, Gulhane Military Medical Academy, 06018, Etlik-Ankara, Turkey ¨ Bioanalytical and Drug DeÕelopment Laboratory, Biological and Medical Research Department (MBC-03), King Faisal Specialist Hospital and Research, PO Box 3354, Riyadh 11211, Saudi Arabia
Received 8 September 1999; received in revised form 15 October 1999; accepted 31 October 1999
Abstract Inclusion complexes of gliclazide with b-cyclodextrin were prepared using different two methods: neutralization and recrysstalization. Host–guest interactions were studied in the solid state by X-ray diffractometry and infrared spectroscopy. The stability constant between gliclazide and b-cyclodextrin was calculated from the phase solubility diagram. It was found that the neutralization technique and a solid complex of gliclazide with b-cyclodextrin in a molar ratio of 1.5:1 could be used to prepare the amorphous state of drug inclusion complexes. The dissolution rates of gliclazide from the inclusion complex made by neutralization was much faster than the pure drug, physical mixture of drug and cyclodextrin, recyristalization system and also comparable to the data reported in literature. Results of this report indicate that b-cyclodextrin could be useful for the solid gliclazide formulations as it may results in a more rapid and uniform release of the drug. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Cyclodextrin; Gliclazide; Dissolution rate; Neutralization; Recrysstalization; Solubility
1. Introduction Cyclodextrins ŽCD. are enzymatically modified starches made up of glucopyranose units. Three different CDs are known. The a-CD consist of six glucopyranose units, b-CD of seven units and g-CD of eight units. All of the CDs are crystalline and nonhygroscopic and they feature a cylinder-shaped, macro ring structure with a large internal axial cavity. The outer surface of a CD molecule is hydrophilic but internal cavity is apolar ŽSaenger, 1980; Szejli, 1988; USP, 1995.. The CDs comprise a family of cyclic oligosaccharides knwon to form noncovalent inclusion complexes with many substances specially with hydrophobic drug molecules. Inclusion complexation of drugs with CDs may be useful to solve various pharmaceutical
) Corresponding author. Tel.: q966-1-442-7859; fax: q966-1-4427858. E-mail address: [email protected] ŽH.Y. Aboul-Enein.. 1 Presented at the 2nd International Meeting on Pharmacy and Pharmaceutical Sciences, September 1998, Istanbul, Turkey.
formulation problems such as imrovement of stability ŽAndersen and Bundgaard, 1984., solubility, dissolution rate ŽPitha et al., 1986; Blanco et al., 1991; Ammar et al., 1999. and bioavailability ŽChow and Karara, 1986; Bekers et al., 1991.. Gliclazide w1-Ž3-Azabicyclo Ž3,3,0.oct-3yl.-3-p-tolylsulphonylureax is a second generation of hypoglycemic sulfonylureas ŽReynolds, 1993.. The major drawback in the therapeutic application and efficacy of gliclazide as oral dosage forms is its very low aqueous solubility because of its hydrophobic nature. It is characterized by low dissolution rate in water. For these reasons, its bioavailability shows interindividual variations as shown by Gillmann et al. Ž1990.. The present study was carried out to investigate the inclusion mode between gliclazide and b-CD in the solid state using X-ray diffractometry ŽXRD. and infrared spectroscopy ŽIR.. Neutralization, recrysstalization and physical mixing were employed for the preparation of gliclazide systems with b-CD and the effect of complexation in the solubility and dissolution rate of gliclazide was evaluated. To date, the solid state characterization and dissolution
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characteristics of gliclazide-b-CD, inclusion complexes have not yet been reported, except in recent works of Moyano et al. Ž1997a,b.. The primary objective of the present study is to investigate the possibility of improving the release properties of gliclazide via complexation with b-CD. Furthermore, the dissolution rate profile and the inclusion complex molar ratio of gliclazide-b-CD system in aqueous media are reported. The investigation suggests that a b-CD complex of gliclazide may be sufficiently soluble to be clinically useful.
2. Experimental 2.1. Materials Gliclazide was a gift from Servier ŽIstanbul, Turkey. and a , b and g-CDs were supplied by Chinoin Pharmaceutical and Chemical Works ŽHungary.. All other chemicals were of analytical grade and supplied by Sigma ŽSt. Louis, MO. or Merck ŽDarmstadt, Germany.. 2.2. Phase-solubility assays The phase-solubility studies for gliclazide were tested with a , b and g-CDs. According to the obtained results, the best solubility of gliclazide was obtained with b-CD. Ten milligrams of gliclazide were accurately weighed into each of 10 ml screw-capped vials to which 10 ml of aqueous solutions containing various concentrations of CD’s Ž0.001–0.01 M. were added. The sealed flasks were shaken at a controlled room temperature of 25 " 0.58C. After equilibration up to 72 h, an aliquot was filtered with a 0.2 mm membrane filter. Aliquot portions of the filtrate were properly diluted and analyzed by UV spectrophotometry at 227 nm. 2.3. Preparation of solid complex The solid complexes of gliclazide with b-CD 1:1, 1:2, 1.5:1 Žmolar ratio. were prepared using neutralization and coprecipitation methods. 2.3.1. Neutralization method One gram gliclazide was accurately weighed and dissolved in 50 ml, 1 N sodium hydroxide solution, followed by 2.33 g b-CD. This mixture was placed on a magnetic stirrer and stirred until a clear solution was obtained. Fifty millilitres 1 N hydrochloric acid was added drop by drop, and the solution was stirred for 2 h with magnetic stirrer. The formed precipitate was separated by vacuum filtration and washed repeatedly and dried at room temperature. 2.3.2. Recrysstalization method Gliclazide was first prepared by adding 1 g of gliclazide to 50 ml of methylene chloride. To this solution 2.33 g of
accurately weighed b-CD was added. This mixture was stirred until a clear solution Žabout 2 h. was obtained. This mixture was placed in a vacuum and the solvent was allowed to evaporate at 408C ŽSaenger, 1980; Seo et al., 1983.. 2.3.3. Preparation of the physical mixtures Physical mixtures of gliclazide with b-CD Ž1:1, 1:2, 1.5:1 molar ratio. were prepared by simple blending in a ceramic morter. 2.3.4. Characterization of the mixtures and the inclusion complexes XRD was carried out using a Philips PW 1730 X-ray generator ŽHolland.. The operation conditions were as follows: X-ray source; Ni-filtered; Cu K a radiation; voltage 40 kV; current 20 mA; time constant 2 s; scanning rate 28 cmy1 . IR was carried out using a Shimadzu IR-470 ŽJapan. model infrared spectrophotometer, according to the KBr disk method. 2.3.5. Dissolution rate studies In vitro dissolution studies of pure drug, physical mixtures and inclusion complexes prepared by the two methods of all complex ratios were evaluated. Dissolution studies for the samples prepared by neutralization and recrystallization method were carried out according to the USP XXIII Ž1995. paddle method ŽCaleva Model 7ST, England.ŽUSP Apparatus 2.. Powder samples containing 10 mg of gliclazide or its equivalent amount of inclusion complexes or physical mixture form were placed in 100 ml of the dissolution medium in a cell at 37 " 0.58C for 12 min. In this assay, 900 ml of dissolution fluid Ž0.1 N HCl, pH 1.2. and stirring rate at 100 rpm were used. At predetermined time intervals, samples were automatically taken for spectrophotometric determination of gliclazide concentration following automatically filtration at 227 nm. All samples were analysed in triplicate. Dissolution efficiencies after 120 min were calculated according to five different kinetics such as, zero-order, first-order, HixsonCrowell, RRSBW and Q y 6t.
3. Results and discussion 3.1. Phase-solubility studies Table 1 shows the effects of 3 CD polymers on the solubility of gliclazide increased in the order of b-CD ) a-CD ) g-CD. The cavity size in the polymer of b-CD seems to be optimum to entrap the gliclazide molecule and consequently provides the greatest solubilization effect. Solubility measurements were carried out according to the method described by Higuchi and Connors Ž1965.. The phase solubility profiles for the complex formation be-
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Table 1 Phase-solubility results of gliclazide in various cyclodextrins Medium
Solubility mgrl
Confidence limits 95%
Relative standard deviation
0.01 M a-cyclodextrin 0.01 M b-cyclodextrin 0.01 M g-cyclodextrin
32.48 35.50 29.13
"0.32 "0.24 "0.48
0.397 0.268 0.669
tween gliclazide and b-CD are presented in Fig. 1. Inclusion complex showed a typical Bs-type solubility curve ŽHiguchi and Connors, 1965., where the initial ascending portion is followed by a plateau region and then a decrease in total gliclazide solubility accompanied by precipitation of a microcrystalline complex. Stability constant of this inclusion complexation was found to be 195 My1 to make use of the stoichiometric calculation for improvement of Bs-type solubility curve. Although the geometrics within the inclusion complexes in aqueous solutions can not be accurately defined, it is reasonable to assume a 1.5:1 M complexation, because this would allow maximum contact of hydrophobic portion of the organic substrate with the apolar cavity of b-CD ŽGriffiths and Bender, 1973.. 3.2. EÕidence of complex formation in solid state To confirm the complexation of gliclazide with b-CD in the solid state, XRD and IR were employed and compared with the corresponding physical mixtures in the same molar ratio. The X-ray diffractograms of gliclazide, b-CD and its binary complexes in comparison with the physical mixtures are shown in Fig. 2. The diffraction pattern for the physical mixture closely resembles that of b-CD, as expected. However, the pattern for the complex differs significantly from that of the physical mixture. Some peaks disappeared, some peaks appeared and some
Fig. 1. Phase solubility diagram of Gliclazide-bCD inclusion complex at room temperature.
Fig. 2. X-ray diffraction patterns of: ŽA. Gliclazide, ŽB. b-CD ŽC., Physical mixture of Gliclazide, and b-CD ŽD. Gliclazide– bCD inclusion complexes by recrystallization method Ž1.5:1., ŽE. Gliclazide– bCD inclusion complexes by neutralization method Ž1.5:1..
peaks height are decreased. The appearance of new peak was observed, indicating the presence of new solid crystalline phases, corresponding to inclusion complexes of the same nature. The functional groups of gliclazide involved in the complexation were also involved in IR. Infrared spectra of the gliclazide and inclusion complexes by recrystallization and neutralization method and physical mixture of gliclazide with b-CD are shown in Fig. 3. Infrared spectrum of gliclazide is characterized by the absorption of the carbonyl ŽC-O. sulphonylurea group at 1706 cmy1 . In the spectra of the inclusion complex, this band was shifted towards higher frequencies at 1725 cmy1 . Also, the NH group which is located at 3265 cmy1 from the IR spectrum of gliclazide was shifted to 3365 cmy1 . The sulphonyl group bands ŽS-O. are located at 1349 cmy1 and 1162 cmy1 in pure gliclazide. In the conclusion complex, the asymmetrically vibration peak of S-O band
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groups are shifted towards higher frequencies, suggesting that after the formation of the inclusion complex existing bonds were broken and also reduced in their intensities. Thus, as spectral changes always concern C–OH, –CH 2 and CH groups of the b-CD, it should be suggested that the host–guest interactions are dominated by hydrogen bonds among the above mentioned groups. 3.3. Dissolution behaÕiour of complexes Fig. 4 shows the dissolution behaviour of gliclazide alone, from inclusion complexes and physical mixtures. The release rate profiles were drawn as the percentage gliclazide dissolved from the inclusion complexes, physical mixture and pure drug versus time. It is evident that both the complexes and physical mixtures exhibit a faster dissolution rate than the free drug. The remarkable increase was for the inclusion complex prepared by the neutralization method rather than the recrystallization method. The amounts of gliclazide dissolved after 5, 10, 25 and 60 min are presented in Table 2. According to the obtained results the inclusion complex prepared by the neutralization method and ratio of the complex 1.5:1 dissolved in 5 min. The drug dissolved very rapidly within the first five minutes and by the end of 10 min 99.25% of drug was dissolved in the gastric medium. The extent of the enhancement of the dissolution rate was found to be dependent on the preparation method, since the neutralization method exhibits the highest dissolution rates all complexation ratios of gliclazide and b-CD. This behaviour may be attributed to the high energetic amorphous state and inclusion complex formation. The small dissolution rate increase found for the physical mixture is only due to the wetting effect of the b-CD. Fig. 3. IR spectra of: ŽA. Gliclazide, ŽB. b-CD ŽC., Physical mixture of Gliclazide and b-CD, ŽD. Gliclazide– bCD inclusion complexes by recrystallization method Ž1.5:1., ŽE. Gliclazide– bCD inclusion complexes by neutralization method Ž1.5:1..
was obtained at between 1394–1342 cmy1 as three decreased intensity peaks. Symmetrically vibration peak of S-O band which is located at 1162 cmy1 was shifted to 1155 cmy1 in pure gliclazide. The IR spectrum of b-CD is characterized by intense bands at 3300–3500 cmy1 , associated with the absorption of the hydrogen bonded-OH groups of b-CD. The vibration of the –CH and –CH 2 groups appear in the 2800–3000 cmy1 region. The observed changes in the infra red spectra of the binary systems may be explained by the different preparation methods. As can be seen in the spectral pattern of the physical mixtures, it corresponds simply to the superposition of the IR spectra of the two components. However, in the neutralization and recrystallization procedures almost total smoothing of the band situated at 3200–3700 cmy1 was observed. Moreover, the vibrations of sulphonylurea
Fig. 4. Dissolution rate profiles of Gliclazide and its b-CD system in 0.1 N HCl at 378C. Žl. Gliclazide Ž'. Physical mixture Ž1.5:1. Žv . Gliclazide b-CD complex by recrystallization method Ž1.5:1. ŽB. Gliclazide b-CD complex by neutralization method Ž1.5:1. Each point: mean" S.D.
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Table 2 Mean percentages of gliclazide dissolved from 1.5:1 molar ratio of inclusion complexes, physical mixture and pure drug after different time intervals in pH 1.2 at 37"0.58C Preparation method
Released percentage of gliclazide"S.D.
Pure gliclazide Physical mixture Recrystallization Neutralization
5 min
10 min
25 min
60 min
10.00"2.77 40.17"1.36 61.55"2.45 97.85"2.40
18.67"1.34 48.36"0.99 69.13"1.46 99.25"1.94
41.16"0.88 61.19"3.76 79.18"1.86 99.87"3.02
47.19"1.34 70.05"4.24 80.29"1.27 100.0"2.35
Five different kinetics such as, zero-order, first-order, Hixson–Crowell, RRSBW, Q y 6t were applied to the results obtained from the dissolution studies of inclusion complexes, physical mixtures and pure drug. The results were evaluated kinetically ŽHiguchi, 1963; Langenbucher, 1976. ŽTable 3.. According to the investigation of the kinetic assessment of the release data, the best released kinetic was found to be RRSBW for all formulations, because of the highest correlation coefficient, lowest AKAIKE’s information criteria and also lowest sum of weighted squared deviations. For RRSBW kinetic, T63.2% , results were obtained 1 min for inclusion complexes; 33.61
min for physical mixture and; 132.43 min for pure gliclazide. According to this kinetic, low b value corresponds with a steeper initial slope followed by a flattened tail in the final part. Actual curves tend to have shape parameters between 0.5 and 2. When no disintegration occurs at all or disintegration is extremely fast, the rate of dissolution will decrease monotonously and the cumulative curve will also be monotonous with b F 1. In this study, shape factor Ž b . obtained from RRSBW was found to be - 1 for all formulations. The release of the drug from inclusion complexes is nearly completed within 10 min for neutralization method.
Table 3 The kinetic assessment of dissolution data kr 0 : Zero-order release rate constant. kr: First-order release rate constant. T : Value stands for the time for 63.2% release of the drug. b : Shape factor. k: Rate constant obtained from Qy6t kinetic. K : Rate constant obtained from Hixson–Crowell kinetic. r 2 : Determination coefficient. AIC: AKAIKE’s information criteria. SWSD: Sum of weighted squared deviations. Applied kinetics
RRSBW
Zero-order
First-order
Hixson–Crowell
Qy6t
Formulations
T63.2% b r2 SWSD AIC kr 0 r2 SWSD AIC kr r2 SWSD AIC K r2 SWSD AIC k r2 SWSD AIC
Gliclazide
Physical mixture Ž1.5:1.
Neutralization method Ž1.5:1.
Recrystallization method Ž1.5:1.
132.43 0.57 0.846 0.055 y23.72 1.77 0.664 0.43 y3.954 0.281 0.737 0.41 y6.53 0.193 0.713 0.258 y10.92 33.47 0.796 0.089 y21.67
33.61 0.328 0.988 0.0038 y48.78 1.648 0.811 0.149 5.65 0.456 0.899 0.137 2.66 0.341 0.871 0.896 y1.67 81.45 0.917 0.480 y9.53
1 0.632 0.914 0.041 y46.71 0.066 0.407 0.41 14.37 9.57 0.855 0.725 9.72 0.966 0.778 0.268 6.28 184.07 0.546 1.55 5.596
1 0.112 0.842 0.033 y33.33 0.708 0.506 3.307 12.35 0.284 0.585 3.32 10.30 0.417 0.558 2.05 4.34 113.22 0.654 y3.94 y0.914
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4. Conclusion The best solid inclusion complexes of gliclazide with b-CD can be obtained by the neutralization method using molar ratio 1.5:1. According to our results from the dissolution rate studies, inclusion complexes prepared by neutralization method exhibits better and faster solubility and dissolution rate profile compared to the reported literature method ŽPitha et al., 1986.. These results are probably due to Ža. the difference in preparation methods, Žb. using b-CD from various manufacturers, and Žc. using different molar ratio for the preparation of the inclusion complexes. The inclusion complexes of b-CD-gliclazide prepared by the neutralization method offers an improvement in the solid pharmaceutical formulations of the drug, which renders it sufficiently soluble for its clinical application.
References Ammar, H.O., Ghorab, M., El-Nahhas, S.A., Emara, L.H., Makram, T.S., 1999. Inclusion complexation of furosemide in cyclodextrins. Pharmazie 54, 142–144. Andersen, F.A., Bundgaard, H., 1984. Inclusion complexation of metronidazole benzoate with b-cyclodextrin and its depression of anhydratehydrate transition in aqueous suspensions. Int. J. Pharm. 19, 189–197. Bekers, O., Uijtendaal, E.V., Beijnen, J.H., Bult, A., Underberg, W.J.M., 1991. Cyclodextrins in pharmaceutical field. Drug Dev. Ind. Pharm. 17, 1503–1549. Blanco, J., Vila-Jato, J.L., Otero, F., Anguiano, S., 1991. Influence of method of preparation on inclusion complexes of naproxen with different cyclodextrins. Drug Dev. Ind. Pharm. 17, 943–945.
Chow, D., Karara, A., 1986. Characterization, dissolution and bioavailability in rats of ibuprofen-b-cyclodextrin complex system. Int. J. Pharm. 28, 95–101. Gillmann, A.G., Rall, T.W., Nies, A.S., Taylor, P., 1990. In: Goodman and Gillmann’s The Pharmacological Basis Therapeutics. 8th edn. Pergamon, Maxwell House, New York, USA, pp. 1485–1486. Griffiths, D.W., Bender, M.L., 1973. Cycloamyloses as catalysts. Adv. Catal. 23, 209–261. Higuchi, T., 1963. Mechanism of sustained action medication. J. Pharm. Sci. 52, 1145–1149. Higuchi, T., Connors, K.A., 1965. Phase-solubility techniques. Adv. Anal. Chem. Instrum. 4, 117–212. Langenbucher, F., 1976. Parametric representation of dissolution rate curves by the RRSBW distrubution. Pharm. Ind. 38, 472–477. Moyano, J.R., Arias-Blanco, M.J., Gines, J.M., Giordano, F., 1997a. Solid-state characterization and dissolution characteristics of gliclazide-b-cyclodextrin inclusion complexes. Int. J. Pharm. 148, 211–217. Moyano, J.R., Arias-Blanco, M.J., Gines, J.M., Rabasco, A.M., PerezMartinez, J.I., Mor, M., Giordano, F., 1997b. Nuclear magnetic resonance investigations of the inclusion complexation of gliclazide with -b-cyclodextrin. J. Pharm. Sci. 86, 72–75. Pitha, J., Milecki, J., Fales, H., Pannell, L., Uekama, K., 1986. Hydroxypropyl-b-cyclodextrin: preparation and characterization; effects on solubility of drugs. Int. J. Pharm. 29, 73–82. Reynolds, J.E.F. ŽEd.., Martindale. The Extra Pharmacopoeia. 30th edn. The Pharmaceutical Press, London, pp. 279–280. Saenger, W., 1980. Cyclodextrin inclusion compounds in research and laboratory. Angew. Chem. Int. Ed. Engl. 19, 344–362. Seo, H., Tsruoka, M., Hashimato, T., Fujinaga, T., Otagiri, M., Uekama, K., 1983. Enhancement of oral bioavailability of spiranolactone by beta and gamma-cyclodextrin complexations. Chem. Pharm. Bull. 31, 286–291. Szejli, J. ŽEd.., Cyclodextrin Technology. Kluwer Academic Publishers, Dordrecht, pp. 1–78. The United States Pharmacopeia, 995. 23rd Revision, Rand Mc Nally, Tounton, MA, pp. 1791–1792, pp. 2220–2221.