title: Amobarbital--a probe of hepatic drug oxidation in man.
abstract: Some aspects of the fate of amobarbital were investigated since this drug is being used as a probe to gauge drug oxidation in man. The mean ratio of orally available over intravenously injected amobarbital was established as 0.99 +/- 0.11 (SD), by comparing integrated concentration-time curves, indicating complete absorption and absence of a first-pass effect. One subject ingested 200 mg of amobarbital sodium, and amobarbital concentrations in serum were monitored for 5 days thereafter. Elimination of amobarbital under these conditions followed first-order kinetics. One subject ingested amobarbital 7 times over a period of 3 yr; plasma clearances (32.1 +/- 1.8 [SD]ml/min) exhibited remarkable constancy, while biologic half-lives (26.5 +/- 3.1 hr) and distribution volumes (73.6 +/- 8.0 L) showed some fluctuation. The distribution of parameters of amobarbital elimination was investigated in 36 unrelated subjects. Amobarbital half-lives (23.8 +/- 6.7 hr) appeared to be normally distributed, while the clearances (36.7 +/- 10.0 ml/min) might not follow a normal distribution.
mesh_terms: D000293:Adolescent; D000328:Adult; D000654:Amobarbital; D001682:Biological Availability; D005260:Female; D006207:Half-Life; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D013997:Time Factors
chemical_list: D004364:Pharmaceutical Preparations; D000654:Amobarbital