Fig. 5.

Simulation of the urine pH effect on methamphetamine (Meth) urinary excretion and plasma concentration-time profile. Methamphetamine urinary excretion profiles (A) and plasma concentration-time profiles (B) were simulated after 11 mg methamphetamine oral administration under acidic urine pH condition (red dashed curves), uncontrolled urine pH condition (black solid curves), and alkaline urine pH condition (blue dotted curves). Simulated Meth urinary excretion as a function of time was compared to observed data (N = 1) under three different urine pH conditions (Beckett and Rowland, 1965c) shown in red squares (acidic urine), black circles (uncontrolled pH urine), and blue triangles (alkaline urine). The calculated AAFE values for all three urine conditions are shown in the insets.