The excretion of hydroxyamylobarbitone in man after oral administration of amylobarbitone and hydroxyamylobarbitone

Abstract

Abstract The excretion of hydroxyamylobarbitone in man has been measured over six days after an oral dose of 200 mg of sodium amylobarbitone. The biological half-life of hydroxyamylobarbitone determined from “Sigma-minus” plots ranged between 16·8 and 22 h in seven subjects, in another subject the half-life was 34·4 h. The effects of increasing urine flow on the amount of hydroxyamylobarbitone excreted after ingestion of 200 mg of sodium amylobarbitone were assessed. A subject normally excreting 34% of the dose as hydroxyamylobarbitone excreted 45% of the dose as metabolite while taking chlorothiazide as a diuretic. With the same subject taking increased fluids to produce a greater urine flow 41% of the dose was excreted as hydroxyamylobarbitone. Hydroxyamylobarbitone is not bound to plasma proteins and when an aqueous solution of 50 mg of hydroxyamylobarbitone was taken by mouth, 57% of the dose was eliminated in the first 8 h and 91% in the first 24 h. The half-life for ingested hydroxyamylobarbitone was 5·7 h, showing that the rate of elimination of this metabolite is faster than its rate of formation when amylobarbitone is ingested.