A novel floating osmotic pump controlled release system （FOP） and traditional matrix sustained release tablets （MT） of dipyridamole （DIP） were characterized in terms of pharmacokinetics, drug release, and in vitro-in vivo correlation. In vivo study was performed by a three-crossover study in six beagle dogs relative to the conventional tablet （CT）. A HPLC method for the determination of DIP in the plasma was developed. Cumulative percent of absorption fraction was compared to that of in vitro cumulative release. Both FOP and MT displayed obvious extended release characteristic in vivo while FOP showed a better extended release behavior. The bioavailability of FOP was higher than that of MT and a zero-order release linear correlation of DIP between fraction absorbed in vivo and fraction dissolved in vitro was established for FOP while not for MT. The results indicated the existence of an absorption window in upper part of the GI track of DIP, which meant that floating system could be excellent for the drug delivery. In addition, the in vitro model was a good choice for depicting in vivo absorption and for optimization of the formulation of FOP if it is needed to be bio-equivalent to MT.
