Influence of hydrophilic polymers addition into cinnarizine–β-cyclodextrin complexes on drug solubility, drug liberation behaviour and drug permeability

The aims of this study were (1) to prepare cinnarizine (CNZ)–β-cyclodextrin (β-CD) complexes by the kneading, co-precipitation and co-evaporation methods with (ternary system) or without (binary system) the addition of two different hydrophilic polymers [hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP)] in their two different grades (HPMC E5-LV or K4M and PVP K-25 or K-30) and (2) to determine the polymers influence on enhancing the CNZ solubility and the in vitro CNZ liberation behaviour or drug permeation characteristics via artificial membrane from the prepared CNZ–β-CD binary and ternary complexes in 0.1 N HCl (pH 1.2). The presence of hydrophilic polymers in ternary complex system did produce irregular-shaped but smooth-surfaced particles while binary complex system (with no polymer addition) did not. The ternary complexes prepared with HPMC K4M, β-CD and CNZ showed higher solubility efficiency value compared to other tested hydrophilic polymers to make ternary complex systems. Consequently, irrespective of the three preparation methods, the ternary complex systems exhibited higher drug libration behaviour in comparison to the binary complex system, physical mixtures and CNZ powder. But because of the possible presence of a solubility and permeability interplay or tradeoff particularly in the binary and ternary complex systems, the CNZ permeation amount in 0.1 N HCl (pH 1.2) via artificial membrane was established to a minimum compared to the CNZ powder. Therefore, the CNZ–β-CD complexes with or without the HPMC and PVP should unequivocally be used with great care by considering the solubility–permeability interplay or tradeoff into account.