The method of separate exponentials: A simple aid to devising intravenous drug-loading regimens

Abstract

Simulation of complex dosage regimens for drugs with multicompartmental kinetics is described using the method of separate exponentials. This approach requires that .alpha.- and .beta.-phases are treated separately throughout and summed only at the end of the simulation. The method was used to devise a loading regimen for pirmenol, comprising a priming injection and a rapid loading infusion, followed by a maintenance infusion. The regimen was tested in a patient with excellent agreement. The method of separate exponentials is mathematically simple and of informational value in that it demonstrates when the early distribution phase is important. Its use can avoid the potentially dangerous assumption of 1-compartmental kinetics in the design of i.v. loading regimens.