Effects of pharmaceutical excipients on the in vitro release rate of sodium salicylate from oily vehicles

The work objective was to study the possible effects of different pharmaceutical excipients on the release of sodium salicylate from oily vehicles. Several formulations of Fractionated Coconut Oil [FCO] containing different pharmaceutical additives were prepared. The release rate behaviour of sodium salicylate from these oily formulations was investigated using a dialysis method. The time required for 30% and 50% of the salicylate to appear in solution outside the dialysis sac [t[30%] and t[50%]] respectively, were used as indices for estimating the release rate. The results of this study showed that the aluminium stearate retards the release rate of salicylate specially when its concentration is 1.5%w/v or more. Oily formulation containing 0.5% w/v aluminium stearate +0.7%w/v lecithin +0.35% w/v hydrogenated castor oil +20% w/v sucrose in FCO and oily formulation containing 0.5% w/v Cab-o-sil + 20%w/v sucrose in FCO delayed the release rate of the drug. However, the inclusion of sucrose in the formulations complicates the situation and enhances the release rate especially at the later stages. The enhancing effect of sucrose on the release rate is nullified by the inclusion of 1% w/v Cab-o-sil. Possible reasons for these effects are discussed with particular reference to the tendency forming globules of sucrose, due to the osmotic effect inside the dialysis sac. Oily formulations [0.5% w/v aluminium stearate + 0.7%w/v lecithin + 0.35% w/v hydrogenated castor oil + 20% w/v sucrose in FCO] and [0.5% w/v Cab-o-sil + 20%w/v sucrose in FCO] can be used as a depot preparations for chronic disease conditions. The enhancing effect of sucrose on the release rate of salicylate can be beneficial if acute response is required. Extrapolation of this study on tablets, capsules and i.m. injection formulations is suggested