Methaqualone-diphenhydramine interaction study in humans

Twelve healthy subjects received three single oral doses (250 mg) of methaqualone alone or in combination with diphenhydramine (25 mg). Blood samples were collected for a 48-hr period after each dose and analyzed for methaqualone and its major metabolite, 2-methyl-3-(2'-hydroxymethylphenyl)-4(3H)-quinazolinone. Peak blood concentrations ranging from 1.0 to 2.7 micrograms/ml occurred approximately 1-2 hr after the oral dose. The area under the blood level-time curve, peak plasma level, and elimination half-life for methaqualone were not significantly different (three-way ANOVA, p greater than 0.05) when methaqualone was administered alone, in combination with a diphenhydramine elixir or as a commercial product (capsule) containing both methaqualone and diphenhydramine. Statistically significant intersubject differences in the area under the curve were eliminated if the area was corrected for subject differences in elimination. Blood levels of the metabolite reached an average peak of 314 ng/ml (+/- 107) between 4 and 8 hr after the dose and remained elevated for the 48-hr sampling period. The areas under the blood level time curve of the metabolite were not significantly different for the three treatments. Diphenhydramine administered at the dosage level used in therapeutic combination products did not alter the blood levels of methaqualone or its metabolite. In addition, no significant differences in methaqualone availability from the two commercial formulations tested could be detected.

Mass screening and confirmation of methaqualone and its metabolites in urine by radioimmunoassay-thin-layer chromatography

A sensitive, rapid, and specific procedure is described for the mass screening and confirmation of methaqualone (Quaalude) in urine specimens. The method is sensitive to 1.0 microgram/ml levels of total methaqualone excretion products (free methaqualone, free hydroxylated methaqualone metabolites, and conjugated hydroxylated methaqualone metabolites). The raw urine is screened directly by radioimmunoassay, which is reactive to all the methaqualone excretion products. Specimens that are screened positive are confirmed by thin-layer chromatography using a solvent system of ethyl acetate-1,2-dichloroethane-chloroform (75:15:10) which separates methaqualone and its four major metabolites without interference from other drugs or urinary substances. The distinctive spot pattern produced by the methaqualone metabolites makes false positive results nearly impossible.

Simultaneous identification and quantitation of diphenhydramine and methaqualone

Methods for the simulataneous identification and quantitation of diphenhydramine and methaqualone in urine have been investigated. Suitable thin-layer and gas chromatographic techniques have been developed. The extraction techniques were evaluated by extracting human urine after the ingestion of therapeutic dosages of the two drugs. A charcoal cartridge technique proved to be superior to direct solvent extraction. Although enzyme hydrolysis gave slightly better recoveries than the charcoal cartridge technique, it is a time-consuming procedure.