A new in vitro technique for the evaluation of drug release profile from colloidal carriers - ultrafiltration technique at low pressure

A new in vitro technique, ultrafiltration at low pressure, is proposed for the evaluation of drug release profile from colloidal carriers such as submicron emulsions and nanoparticles. A thorough description is given after having reviewed the various available techniques for drug release evaluation from colloidal carriers. The results yielded by the new technique clearly show that miconazole release from either the submicron emulsion or a marketed micellar aqueous solution was very rapid under perfect sink conditions. This fact raised doubts and practically rules out the possibility of using submicron emulsions as a controlled-release drug delivery system for i.v. administration. The in vitro indomethacin release profile from PLA or PLGA nanoparticles was found to be biphasic with an immediate release of 40-80% of the initial drug concentration, followed by a slower exponential release which lasted a few hours. It was deduced from the overall kinetic results that the ultrafiltration method at low pressure was versatile, sensitive and capable of distinguishing between different kinetic behaviors. The technique offers the possibility of identifying the underlying release mechanism of drug from colloidal carriers.