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 su ch 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 th e new technique clearly show that miconazole release from either the s ubmicron emulsion or a marketed micellar aqueous solution was very rap id under perfect sink conditions. This fact raised doubts and practica lly rules out the possibility of using submicron emulsions as a contro lled-release drug delivery system for i.v. administration. The in vitr o indomethacin release profile from PLA or PLGA nanoparticles was foun d to be biphasic with an immediate release of 40-80% of the initial dr ug concentration, followed by a slower exponential release which laste d a few hours. It was deduced from the overall kinetic results that th e ultrafiltration method at low pressure was versatile, sensitive and capable of distinguishing between different kinetic behaviors. The tec hnique offers the possibility of identifying the underlying release me chanism of drug from colloidal carriers.