Comparison of methaqualone excretion patterns using abuscreen ONLINE and EMIT II immunoassays and GC MS

Abstract A study was performed to compare the ONLINE and EMIT II immunoassays with gas chromatographic/mass spectrometric ( GC MS ) analysis of methaqualone metabolites on urine using samples obtained from a clinical study. Urine was collected over a 72 h period from six healthy adults (4 male, 2 female) after oral dosing with 200 mg methaqualone (MTQ). Each urine sample was analyzed by ONLINE and EMIT II. The samples were then analyzed by GC MS , hydrolyzed with beta-glucuronidase and again analyzed by GC MS . Both immunoassays showed greater than 600 ng/ml concentrations of drug in each sample by the second void and remained highly positive for the rest of the 72 h. Unhydrolyzed samples analyzed by GC MS showed both low concentrations of MTQ as well as its five major hydroxylated metabolites. The hydrolyzed samples analyzed by GC MS showed high concentrations of the hydroxylated metabolites with the 2′-hydroxy and 3′-hydroxy metabolites being present at the highest concentrations, the 4′-hydroxy metabolite at a lower amount and the 6-hydroxy and 2-hydroxy metabolites at the lowest concentrations. The GC MS data coupled with the antibody cross-reactivity data indicate that the major species in clinical samples that cross-react in both immunoassays are the conjugated forms of the hydroxylated metabolites of MTQ. Therefore when confirming by GC MS after an immunoassay screen it would be prudent to confirm for the major hydroxylated metabolites as glucuronides of MTQ instead of the parent drug.