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

Controlled release dosage forms offer advantages over conventional dos age 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, lea ding often to major differences. The process of drug release from a dr ug-polymer device controlled by diffusion is established with either a n in vitro or in vivo case. A numerical model taking all the known fac ts into account is built into these two cases. For the in vivo test, t he parameters of interest are the diffusivity, the concentration of dr ug and dimension of the dosage form, the volume of liquid in the stoma ch, the volume of blood, and the rate constants of absorption and elim ination. The results are obtained with the concentration-time historie s of the drug in the stomach and in the blood.