Chitosan based pentazocine microspheres for intranasal systemic delivery: development and biopharmaceutical evaluation.

Bioadhesive chitosan microspheres (Ms) of pentazocine (Pz) for intranasal systemic delivery were prepared with the aim of avoiding the first pass effect, and thus improving the bioavailability and achieving sustained and controlled blood level profiles, as an alternative therapy to injection and to obtain improved therapeutic efficacy in the treatment of chronic pain such as cancer, trauma and post-operative pain, etc. The formulation variables were drug loading, polymer concentration, stirring rate during crosslinking and oils. The microspheres (Ms) were subjected to evaluation for physical characteristics, such as particle size, incorporation efficiency, swelling ability, in vitro bioadhesion, in vitro drug release characteristics and in vivo performance in rabbits. Application of in vitro data to various kinetic equations indicated matrix diffusion controlled drug delivery from chitosan Ms. Drug loading, polymer concentration and stirring speed influenced the drug release profiles significantly while oils had negligible effect. In vivo studies indicated significantly improved bioavailability of Pz from Ms with sustained and controlled blood level profiles as compared to i.v., oral and nasal administration of drug solution. Good correlation was observed between in vitro and in vivo data.