The determination of mean residence time using statistical moments: it is correct

The present communication seeks to end a controversy created by a recent publication regarding the applicability of statistical moment principles for determination of mean residence time of drug in the body tb. It is shown that the equation tb = AUMC/AUC is correct when applied to pharmacokinetic systems in which the total drug elimination rate is directly proportional to the drug concentration in the systemic circulation, i.e., first-order central elimination. More general equations for tb in terms of elimination rate, amount eliminated, and amount in the body are presented along with demonstrations of their utility.