Inter- and intra-individual variation in the metabolism of methaqualone in man after a single oral dose

Summary The urinary excretion of fiveC-monohydroxy metabolites and theN-oxide metabolite of methaqualone in the 24h period immediately after oral dosing with 250 mg methaqualone (Melsed) has been measured in nineteen healthy adults (13 male, 6 female) to assess interindividual variations and in five adults (3 male, 2 female) on five separate occasions to assess intraindividual variations. The overall importance of the six metabolites was 4-hydroxy N-oxide 2-hydroxymethyl > 3-hydroxy > 6-hydroxy = 2-hydroxymethyl. Variations in this order both within the 24h period and within each of the three eight-hour periods constituting the 24 hours were minor and variations in the absolute amount of each metabolite excreted ranged from two to three-fold. Intraindividual variations were generally smaller than interindividual variations and for each individual the pattern of metabolism was similar on the five occasions. There is evidence that theC-oxidation of methaqualone may be more sensitive to cyclical variations in hormone levels than isN-oxidation.