Disposition of hexobarbitone in healthy man: kinetics of parent drug and metabolites following oral administration

N P Vermeulen, C T Rietveld, D D Breimer

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1 Hexobarbitone plasma kinetics were determined in six healthy volunteers, who received 500 mg hexobarbitone orally. In addition urinary excretion rate and cumulative excretion were measured of its three major metabolites: 3'-hydroxyhexobarbitone, 3'-ketohexobarbitone and 1,5-dimethylbarbituric acid. 2 The mean plasma elimination half-life of hexobarbitone was 3.7 +/- 0.9 h (n = 6). Assuming complete absorption, the volume of distribution and the metabolic clearance were 81.3 +/- 20.5 1 and 16.4 +/- 2.9 1/h, respectively. The mean maximal plasma concentration was 7.1 +/- 2.1 micrograms/ml and was reached 1.2 +/- 0.4 h after drug administration. 3 3'-Hydroxyhexobarbitone and 3'-ketohexobarbitone, which are products of allylic side-chain oxidation of hexobarbitone, were excreted in 24 h to the extent of 4.7 +/- 1.3 and 32.1 +/- 11.9% of the dose, respectively. In the same period, 1,5-dimethylbarbituric acid, which is the end product of the epoxide-diol pathway, was excreted to 18.0 +/- 7.8% of the dose. The ratio of the sum of 3'-hydroxy- and 3'-ketohexobarbitone vs 1,5-dimethylbarbituric acid excreted varied with time and amounted ultimately in 24 h urine to 2.3 +/- 1.0. 4 The half-lives of 3'-hydroxyhexobarbitone and 1,5-dimethylbarbituric acid, calculated from their renal excretion rate curves, amounted 5.2 +/- 0.9 and 6.6 +/- 1.3 h and were significantly longer than the half-life of hexobarbitone in plasma. The half-life of 3'-ketohexobarbitone was 4.2 +/- 0.8 h. The maximum excretion rate of 1,5-dimethylbarbituric acid was reached at 7.7 +/- 1.0 h after administration of hexobarbitone. 3'-Hydroxy- and 3'-ketohexobarbitone were excreted with a maximal rate at 2.2 +/- 0.8 and 2.8 +/- 0.4 h respectively.

Original languageEnglish
Pages (from-to)459-64
Number of pages6
JournalBritish Journal of Clinical Pharmacology
Issue number4
Publication statusPublished - Apr 1983


  • Administration, Oral
  • Adult
  • Barbiturates
  • Half-Life
  • Hexobarbital
  • Humans
  • Kinetics
  • Male
  • Metabolic Clearance Rate
  • Journal Article


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