Bioactivity and its measurement

International audienceIn order to characterize quantitatively the property of bioactivity, parameters have to be introduced. In particular, “absolute bioavailability” was defined as the quantity and rate that characterize the transfer of the drug in blood, and “relative bioavailability” as a measurement of the quantity and speed that characterize the transfer of a drug when many forms are compared with a reference form. This chapter introduces the concepts of “absolute compound release” and “instant compound release”, and derives the concept of “matrix effect” from them. Whereas the dynamic compound release describes the exchange of the compounds as a function of time, the dynamic matrix effect describes the variation of the rate at which a compound is released. The analytical method called in situ quantitative nuclear magnetic resonance was proposed for this purpose, based on the fact that gels are colloidal systems that enclose a liquid component