[A simple method for predicting equality of absorption and elimination rate constants].

A new method is proposed by which one can predict whether absorption rate constant (Ka) and elimination rate constant (Ke) are equal in the one-compartment open model with first-order processes. The method used only blood drug concentration-time data in the terminal segment of concentration versus time curve is described as follows. We defined Ai as Ai = 2/(tn + 1 + tn) + ln(cn/cn + 1)/(tn + 1 - tn) (i = 1,2,3,...) where n is the number of sampling sequence, cn and cn + 1, tn and tn + 1 are any two consecutive blood drug concentration (c)-time (t) data in the terminal segment of c-t curve, respectively. If Ai was equal or approximate, Ka and Ke might be equal or approach each other. In addition, both Ka and Ke were equivalent to the arithmetic mean of Ai. If Ai was reduced gradually while (tn + 1 + tn)/2 was increased, Ka might not be equal to Ke.