Abstract

Complex formation of nifedipine with β-cyclodextrin and hydroxypropyl β -cyclodextrin was studied. The possibility of improving the solubility and dissolution rate of nifedipine via complexation with the above cyclodextrins and the feasibility of employing nifedipine cyclodextrin inclusion complexes in the design of mucoadhesive tablets for sustained release were also investigated. The phase solubility studies indicated the formation of a nifedipine- β-cyclodextrin (1:1 M) and nifedipine-hydroxypropyl β -cyclodextrin (1:1 M) inclusion complexes with a stability constant of 121.9 M-l and 253.7 M-I respectively. The solubility and dissolution rate of nifedipine were rnarkedly enhanced by complexation with β-cyclodextrin and hydroxypropyl β -cyclodextrin. Nifedipinehydroxypropyl β -cyclodextrin (1:3) gave highest enhancement (44.8 fold) in the dissolution rate of nifedipine. Mucoadhesive tablets formulated employing nifedipine alone gave very low dissolution. Whereas those formulated employing nifedipine- β-cyclodextrin and nifedipine-hydroxypropyl β-cyclodextrin complexes gave slow, controlled and complete release spread over a period of 12 h. Drug release from these tablets followed zero order kinetics upto 85-90% release and the release was diffusion controlled. Good sustained release two layered tablet formulations of nifedipine, satisfying the theoretical sustained release need based on its pharmacokinetics, were developed using nifedipine-β-cyclodextrin and nifedipine-hydroxypropyl β -cyclodextrin inclusion complexes.