International Journal of Pharmaceutics 228 (2001) 33 – 41 Controlled release of antifungal drug terbinafine hydrochloride from poly(N -vinyl 2-pyrrolidone/itaconic acid) hydrogels Murat S ¸ en *, Arzu Yakar Department of Chemistry, Polymer Chemistry Diision, Hacettepe Uniersity, 06532 Beytepe, Ankara, Turkey Received 9 April 2001; received in revised form 3 July 2001; accepted 9 July 2001 Abstract Adsorption and controlled release of terbinafine hydrochloride (TER-HCl) to and from pH-sensitive poly(N-vinyl 2-pyrrolidone/itaconic acid) P(VP/IA) hydrogels were investigated. P(VP/IA) hydrogels were prepared by irradiating the ternary monomer mixtures of N-vinyl 2-pyrrolidone/itaconic acid/ethylene glycol dimethacrylate in aqueous solution by -rays at ambient temperature. Hydrogels containing antifungal drug TER-HCl, at different drug-to-poly- mer ratios, were prepared by direct adsorption method. The influence of IA content in the gel on the adsorption capacities of hydrogels and the effect of pH on the releasing behavior of TER-HCl from the gel matrix were investigated. Terbinafine adsorption capacity of hydrogels was found to increase from 6 to 82 mg of TER-HCl per gram of dry gel with increasing drug concentration and amount of IA in the gel system. In-vitro drug-release studies in different buffer solutions showed that the basic parameters affecting the drug-release behavior of hydrogels are the pH of the solution and the IA content of the hydrogel. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Terbinafine hydrochloride; Poly(N-vinyl 2 pyrrolidone/itaconic acid); Hydrogels; pH-sensitive www.elsevier.com/locate/ijpharm 1. Introduction Poly-electrolytes are polymers that contain rela- tively high concentrations of ionizable groups along the backbone chain. Poly-electrolytes are distinguished from a related class of polymers, ionomers, by the density of ionizable groups. Ionomers contain a relatively low concentration of ionizable groups (less than a few mole% of repeating units), while poly-electrolytes contain ionizable groups at levels ranging anywhere from a few mole % to 100 of the repeating units (Brondsted and Kopecek, 1992; Karadag ˘ et al., 1994; Ende and Peppas, 1997; Siegel and Fire- stone, 1988; Kou et al., 1988; Sarı, 2000). The unique properties exhibited by poly-elec- trolytes have led to their application in biomedical systems. Many biomedical applications of poly- electrolytes ultimately arise from their propensity to bind with oppositely charged surfaces and to associate to form complexes with oppositely charged polymers. For example, cationic poly- * Corresponding author. Tel.: +90-312-2977989; fax: +90- 312-2977989. E-mail address: msen@hacettepe.edu.tr (M. S ¸ en). 0378-5173/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S0378-5173(01)00804-3