Exploratory studies on the in vitro release and bioavailability of dextropropoxyphene from lipophilic and hydrophilic suppositories

Abstract

The rectal bioavailability of propoxyphene has been investigated in an explorative study on six volunteers after administration of hydrophilic and lipophilic suppositories with and without a mucoadhesive. A tablet formulation was used as reference. The in vitro dissolution characteristics of the four different rectal compositions were studied by using the basket, paddle and flow-through techniques in order to determine whether these methods could be used to predict the plasma concentration vs time curves. The results indicate that rectal administration of dextropropoxyphene napsylate reduces first-pass elimination of the drug. By choosing a hydrophilic suppository base it was possible to achieve the same rate of absorption and a 60% greater extent of bioavailability of propoxyphene than after oral administration. The basket method was the most suitable technique to predict a ranking between the different compositions.