Distribution and excretion of methamphetamine and its metabolites in rats.  III.  Time-course of concentrations in blood and bile, and distribution after intravenous administration. 
The time-course of blood total radioactivity after i.v.  administration of 3H-methamphetamine to rats showed a biphasic curve.  The biological half-life of the alpha phase (t alpha 1/2) was 6.8 +/- 2.0 min, and that of the beta phase (t beta 1/2) was 11.3 +/- 0.8 h. The major metabolite in the blood was unconjugated p-hydroxymethamphetamine.  The total radioactivity in bile peaked at 1.5 h after i.v.  administration.  The major metabolite in the bile was p-hydroxymethamphetamine glucuronide.  The major compound excreted in urine was unchanged methamphetamine.  Whole-body autoradiography was performed using 14C-methamphetamine, and tissue 3H concn.  was determined after i.v.  administration of 3H-methamphetamine to rats.