Oral osmotic pumps for poorly water soluble drug - Rofecoxib: Formulation development perspective

Abstract

Solid dispersions of poorly water soluble drug, rofecoxib (Rc), using PVP K-30 were first prepared to enhance the dissolution rate of rofecoxib and then the dispersions were fabricated as elementary osmotic pump tablets with an objective to achieve controlled release of rofecoxib that can provide improved therapy with better patient compliance. X-ray diffractometry (XRD) and Differential Scanning Calorimetry (DSC) confirmed the presence of rofecoxib in solution form in the polymeric carrier accounting for the increase in solubility. Infra Red (IR) spectra indicated non-interaction between drug and the carrier. Solid dispersion gave fast and rapid dissolution of rofecoxib compared to pure drug. Osmotic tablets were prepared using drug and solid dispersions separately. Prepared osmotic tablets were evaluated for various physical parameters and in vitro drug release characteristics. Effect of formulation variable (pure drug, different solid dispersions, various osmogen and osmopolymer in core, coating membrane type, coating thickness and orifice diameter) and dissolution condition variables (different speed of agitation) were investigated to test the delivery performance of osmotic tablets. The drug release from OP tablets were observed to be dependent on solid dispersions, type and thickness of coating membrane, various types of osmogens and osmopolymer, but were independent of orifice size and stirred conditions of release medium. OP tablets could provide prolonged, controlled and GI environmental independent rofecoxib release that may result in an improved therapeutic efficacy and patient compliance.