Properties of the recirculation model: Calculation of the amount of drug in the body from blood concentration data, with application to absorption rate calculations

Abstract

Compartment models express the relationship between amounts and concentrations by volumes of distribution, which are fundamental parameters of the models. For a recirculation model, the amount of drug in the body is given by the convolution of the measured blood concentration with a function, termed the retention function, which is a characteristic of the system. The amount of drug in the body can be partitioned into rapidly recirculating and slowly recirculating portions, which are analogous to the amounts of drug in the central and peripheral compartments of a compartment model. A method of calculating absorption rates is presented that is comparable with the Wagner-Nelson and Loo-Riegelman methods, but makes fewer assumptions.