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.