MODELING THE PROCESS OF CONTROLLED-RELEASE OF DRUG IN IN-VITRO AND IN-VIVO TESTS

Controlled release dosage forms offer advantages over conventional dosage forms, in a particular, a more constant and prolonged therapeutic effect. In vitro and in vivo testing is used to determine the release of the drug, and correlations are attempted between these results, leading often to major differences. The process of drug release from a drug-polymer device controlled by diffusion is established with either an in vitro or in vivo case. A numerical model taking all the known facts into account is built into these two cases. For the in vivo test, the parameters of interest are the diffusivity, the concentration of drug and dimension of the dosage form, the volume of liquid in the stomach, the volume of blood, and the rate constants of absorption and elimination. The results are obtained with the concentration-time histories of the drug in the stomach and in the blood.