Long-term urinary excretion of methaqualone in a human subject |
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Authors: | Henry A Heck Kathleen Maloney Michael Anbar |
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Institution: | (1) Mass Spectrometry Research Center, Stanford Research Institute, Menlo Park, California;(2) Present address: Chemical Industry Institute of Toxicology, P.O. Box 12137, 27709 Research Triangle Park, North Carolina;(3) Present address: Department of Pharmaceutical Chemistry, University of California, 94143 San Francisco, California;(4) Present address: Department of Biophysical Sciences, State University of New York at Buffalo, 14226 Amherst, New York |
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Abstract: | The urinary excretion rates of methaqualone and of one of its metabolites, 6-hydroxymethaqualone (free and conjugated), were determined in a normal male subject over a 30-day period by stable isotope dilution analysis using field ionization mass spectrometry. The excretion rates for methaqualone were fitted by computer to three-and four-exponential functions. The estimated terminal halflife for the drug was approximately 74 hr. 6-Hydroxymethaqualone excretion in the elimination phase was fitted to a single exponential decay curve. Estimated halflives obtained for the free and total (primarily conjugated) metabolite were 78 and 70 hr, respectively. The apparent difference between the latter two values was not statistically significant. The close similarity between the halflives of methaqualone and 6-hydroxymethaqualone indicates that elimination of these compounds is ratelimited by the same pharmacokinetic process. A similarly long halflife, 50 hr, was estimated in a previous study (5) of another subject in which excretion of the compounds was followed over an 11-day period. These results demonstrate that the half-life of methaqualone can be much longer than has been indicated by relatively short-term investigations.Supported by Contract DADA17-73-C-3063 from the U.S. Army Medical Research and Development Command. |
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Keywords: | drug metabolism long-term pharmacokinetics mass spectrometry MLAB methaqualone 6-hydroxymethaqualone stable isotopes urinary excretion |
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