Effects of several factors on urinary excretion of methamphetamine and its metabolites in rats.

Effects of dose, route of administration, and sex and strain differences on the metabolism of methamphetamine in vivo were investigated in rats. Excretion of p-hydroxymethamphetamine was decreased with increasing dose of methamphetamine, while that of unchanged methamphetamine and amphetamine increased with dose. Subcutaneous injection instead of oral administration of methamphetamine increased the urinary excretion of unchanged drug and amphetamine, and decreased the excretion of p-hydroxymethamphetamine. No marked sex difference was observed in the urinary excretion of methamphetamine and metabolites. The Donryu strain of rats excreted unchanged methamphetamine and p-hydroxylated metabolites to a lesser extent than did Sprague-Dawley and Wistar strains.