EXPLORATORY STUDIES ON THE IN-VITRO RELEASE AND BIOAVAILABILITY OF DEXTROPROPOXYPHENE FROM LIPOPHILIC AND HYDROPHILIC SUPPOSITORIES

The rectal bioavailability of propoxyphene has been investigated in an explorative study on six volunteers after administration of hydrophil ic and lipophilic suppositories with and without a mucoadhesive. A tab let formulation was used as reference. The in vitro dissolution charac teristics of the four different rectal compositions were studied by us ing the basket, paddle and flow-through techniques in order to determi ne whether these methods could be used to predict the plasma concentra tion vs time curves. The results indicate that rectal administration o f dextropropoxyphene napsylate reduces first-pass elimination of the d rug. By choosing a hydrophilic suppository base it was possible to ach ieve the same rate of absorption and a 60% greater extent of bioavaila bility of propoxyphene than after oral administration. The basket meth od was the most suitable technique to predict a ranking between the di fferent compositions.