Studies on the mechanism of interaction between methamphetamine and quinine in rats.

Interactions between methamphetamine and quinine were studied using two different tests. The duration and intensity of methamphetamine-induced stereotyped behavior was enhanced by pretreatment of rats with quinine. Pretreatment of rats with SKF-525A and CCl4 also resulted in the enhancement of methamphetamine-induced stereotyped behavior. Pretreatment with phenobarbital shortened the stereotypy evoked by methamphetamine. Furthermore, urinary excretion patterns of methamphetamine and its metabolites were determined following the administration of the drug to rats which had been pretreated with certain drugs. Quinine, SKF-525A and CCl4 inhibited the urinary excretion of p-hydroxylated metabolites and increased the excretion of the unchanged methamphetamine and amphetamine. These results strongly suggest that the enhancement of methamphetamine-induced stereotyped behavior in the rats pretreated with quinine, SKF-525A and CCl4 could be ascribed to the inhibition of the p-hydroxylation reaction of methamphetamine and thus may lead to the increased concentration and pharmacological effect of the drug.