Preformulation Studies On Celecoxib With A View To Improve Bioavailability
The present study has three primary objectives. Firstly, in view of the low aqueous solubility of celecoxib, solid dispersions of the drug were prepared and evaluated. Different carriers were chosen and a constant drug to carrier ratio was maintained. The solid dispersions obtained were subjected to solubility and dissolution studies including dissolution rate and efficiency. The best carrier was polyvinylpyrrolidone-vinyl acetate co-polymer, as it increased the solubility by a factor of ten. It also exhibited marked increase in the dissolution rate and efficiency. Secondly, the effect of the surfactant sodium lauryl sulphate on the dissolution rate of celecoxib was investigated. The solubility of a poorly soluble drug is one of the most important factor influencing its dissolution rate and bioavailability. Presence of a surfactant in the dissolution medium permits an experimental situation similar to in vivo conditions and hence results in meaningful in-vitro observations. Dissolution study was conducted using various concentrations of sodium lauryl sulphate employing USP dissolution rate testing apparatus 1. Ultimately, a dissolution medium, which gave reproducible results in vitro was designed. Finally, possible drug excipient interactions between celecoxib and the commonly used excipients including those used in the preparation of its solid dispersions were investigated by storing their respective mixtures at various temperatures and humidity conditions followed by evaluating them with reference to physical and chemical stability and the results were confirmed by IR and DSC spectral studies. Polyvinylpyrrolidone was found to be the most satisfactory excipient. Degradation was evident with all other excipients studied although only at elevated temperatures.