Methaqualone pharmacokinetics after single- and multiple-dose administration in man

Serum levels of methaqualone (MTQ) were determined in eight unfasted subjects following single- and multiple-dose administration of 1×300 mgtablet over a 28-day period. Data were analyzed by a two-compartment open model. Following a fairly rapid absorptive phase (K _a =0.82±0.32 hr^–1),the serum elimination curve was biexponential, consisting of a phase predominantly due to distribution (=0.97±0.55 hr^–1)and a phase predominantly due to elimination (=0.036±0.004 hr^–1).A steady-state MTQ serum concentration profile was observed within the first week. There were no significant changes in the kinetics of absorption, distribution, or elimination over the 28-day period of drug administration. Urinary D-glucaric acid excretion, which increased two-to threefold after the first week of MTQ dosing, returned to normal levels when the drug was discontinued. The significance of the pharmacokinetic parameters in relation to bioavailability and biological disposition of single and multiple dose MTQ administration is discussed.