Using a newly developed sensitive gas chromatograph-mass spectrometer assay for benzquinamide, pharmacokinetics have been determined in man follovnng the administration of intramuscular, oral, and rectal suppository doses. Drug is absorbed most rapidly from the intramuscular dose and least rapidly from suppositories. The mean apparent elimination half-life is 1.0–1.6 hr from all formulations. Benzquinamide is 33–39% bioavailable from the capsule and suppository formulations, relative to the intramuscular formulation. A high correlation between capsule and suppository bioavailabilities suggests that first-pass metabolism may account for at least part of the incomplete availabil