Methaqualone metabolites in human urine after therapeutic doses.

We measured five principal metabolites of methaqualone in the urine of seven volunteers after single and multiple doses of the drug. Urine, collected for up to 72 hours after the last dose, was analyzed for methaqualone and its principal metabolites by high-resolution capillary-column gas chromatography. The major biotransformation of methaqualone under therapeutic conditions occurred through benzylic and para-hydroxylation of the o-tolyl moiety. Methaqualone itself was present in concentrations of no more than 1 mg/liter, if it could be detected at all. The observed physiological effects ant total urinary excretion of metabolites reflected the cumulative nature of the parent drug when it was administered in multiple doses. No clear relationship was found between appearance of a specific metabolite and time after ingestion of the drug, although higher amounts of 2-methyl-3-(2'-hydroxymethylphenyl)-4(3H)-quinazolinone were noted in those individuals who tolerated the drug less well.