Assessment of blood level with controlled-release dosage forms: Effect of the rate constant of elimination of the drug

Abstract

Prediction of the drug level in the volume of distribution was made using a numerical model taking into account the following facts: the kinetics of drug release out of the dosage form along the gastrointestinal tract, the kinetics of absorption in the blood compartment and the kinetics of elimination. Various parameters intervene significantly for a given dosage form. Some emphasis was placed upon the rate of elimination of the drug which appears to be the main characteristic for the drug, especially when it is delivered through controlled release dosage forms. The rate of release of the drug out of the dosage form, as well as the dose frequency and the gastrointestinal transit time were also considered. The drug level in the plasma was expressed by the amount of drug as a fraction of the amount of drug initially located in the dosage form.

Structure and prolonged transport in a biodegradable poly(R-3-hydroxybutyrate)-drug system

“…1b). It is well known that the release of drugs from chemically stable polymer systems occurs via the dif fusion mechanism [37][38][39], whereas biodegradable polyesters with unstable chemical bonds (even in the absence of enzymes) can experience hydrolysis in aqueous solutions, specifically via the mechanism of end group autocatalysis [40]. The characteristic signs of hydrolysis are a loss in the total weight of the sam ple; a decrease in its viscosity average molecular mass; and, after prolonged hydrolysis, a change in the degree dr 0 0 a c of crystallinity (as was shown for PHB, its copolymer with 3 oxyvalerate, polylactides, and PHB-polylac tide mixtures [19,41]).…”