An area function method for estimating the apparent absorption rate constant.

A new method for calculation of the apparent absorption rate constant of a drug has been derived based on the relationship between the plasma concentrations after an oral dose and the area intervals under both the oral and the intravenous plasma concentration-time curves. The method is a noncompartmental technique evolved from the convolution integral and does not use any theoretical approximation. It has been evaluated and compared with nonlinear regression analysis using NONLIN84 and moment analysis using both errorless and errant data. The approach is as adequate as nonlinear regression analysis under a variety of conditions but offers ease and simplicity in handling experimental data.