Prediction of apparent volume of distribution in obesity

A standard height-weight table permits the separation of the obese body into two compartments: a lean and a fat. Depending upon the physicochemical properties of a drug, such as pKa, apparent partition coefficient and extent of protein binding, the distribution of a drug could either be in the lean compartment or in the whole body. Based on this thesis, several equations, either published in the literature or developed for this report, all based on the physico-chemical properties of a drug and the physiological changes in the obese subject, were used to compare the apparent volume of distribution, Vz as predicted by these equations with the Vz values of several drugs reported in the literature for obese subjects. Duncan's multiple range test was used for testing literature values vs. predicted data. Examples from the literature are reported and discussed. The validity of these equations needs to be verified as more information on pharmacokinetic parameters in obesity becomes available.