Urinary excretion pattern of methaqualone metabolites in man.

A method based on selected ion monitoring for determination of five monohydroxy metabolites of methaqualone in urine has been worked out. By means of this method the time course of metabolite excretion was studied in three healthy volunteers receiving an oral therapeutic dose of methaqualone. In all subjects the main monohydroxy metabolite was conjugated 4'-hydroxymethaqualone, but the relative importance of the five metabolites showed intersubject variation. Metabolite excretion was still going on, when urine sampling was discontinued after 70 hr. Only small amounts (less than 1% of the dose during 70 hr) of unmetabolized methaqualone were excreted. On the other hand, it was confirmed that methaqualone-N1-oxide is an important metabolite. The presence of a hydroxy methoxy metabolite of methaqualone, very probably 4'-hydroxy-5'-methoxymethaqualone, as a minor metabolite was established by comparison with authentic, synthetic material. 8-Hydroxymethaqualone and 2-nitrobenz-o-toluidide, reported by other groups, could not be detected.