The kinetics of the urinary excretion of the N-oxide and glucuronides of methaqualone in man

DARK Classics in Chemical Neuroscience: Methaqualone

Commonly known as "Quaaludes," methaqualone (1) is a sedative-hypnotic medication, with effects resembling barbiturates and other downers, that exerts its effects through modulation of γ-aminobutyric acid type A receptors (GABA_AR). Following the discovery of the sedative and euphoric effects of methaqualone (1), it was quickly adopted by pharmaceutical companies and promoted by clinicians around the world as a "safe" sleeping pill option, and for a period it was available over the counter. The popularity of methaqualone (1) soared worldwide, and many people began to use it recreationally for its sedative-hypnotic-like psychoactive effects. Not long after its introduction, many individuals began to misuse the drug leading to overdoses and drug dependence which brought to light methaqualone's (1) addictive nature. In this review, the background, synthesis, pharmacology, metabolism, and pharmacokinetics of methaqualone (1) will be covered along with its discovery, history, and the derivatives that are currently available around the world through manufacture in clandestine laboratories.

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

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.

The effect of age on the competitive C- and N-oxidative pathways of methaqualone in women

The urinary excretion of the N-oxide and the glucuronides of five C-monohydroxy metabolizes of methaqualone has been studied in a group of young women aged 24-34 years and in a group of elderly women aged 85-87 years. The rate of appearance of the metabolites in the urine was slower in the elderly group but the relative importance of the six metabolites was the same in the two groups. There were differences in some metabolite ratios between the two groups, but only one difference approached statistical significance. The metabolite excretion in a 80 year old woman who had received methaqualone daily for over ten years was consistent with that of the elderly group. The results indicate that the ageing process per se and chronic weak hepatic enzyme induction in the elderly are not accompanied by changes in the relative importance of competitive metabolic pathways.

The influence of the menstrual cycle on the metabolism and clearance of methaqualone

1 The rate of methaqualone metabolism in women was shown to be significantly increased at the time of ovulation. 2 The apparent first order rate constants for the formation of five C-monohydroxy metabolites of methaqualone on day 15 of the menstrual cycle were approximately double that on day 1. 3 The N-oxidation of methaqualone showed considerable inter-individual variation in its sensitivity to the menstrual cycle, and in a group of ten women the difference in N-oxide excretion between days 1 and 15 was not statistically significant. 4 The serum clearance of methaqualone on day 15 was higher (mean value 94.6 ml min-1 on day 1, 176.0 ml min-1 on day 15), serum half-life shorter (mean t1/2 beta 16.3 h on day 1, 11.6 h on day 15) and the AUC alpha smaller (mean value 44.0 micrograms ml-1 h on day 1, 24.4 micrograms ml-1 h on day 15) than on day 1. 5 The relative importance of the five hydroxy metabolites was unchanged during the menstrual cycle but the C/N oxidation ratio was greater on day 15 than on day 1. 6 The data for methaqualone metabolism in a control group of men was similar to than in women on day 1 of a menstrual cycle.