Disposition of methadone in methadone maintenance

Clin Pharmacol Ther. 1975 Mar;17(3):258-66. doi: 10.1002/cpt1975173258.

Abstract

Six detoxified opiate addicts housed in a closed metabolic ward received methadone in stepwise increasing doses of 10, 20, 40, and 80 mg/day during 1 month. Four were given 14C-methadone at the lowest dose and again at the highest dose. Of the subjects receiving radiomethadone, 2 excreted the major part of the radioactivity in urine and 2 about equally in urine and feces. In addition to methadone, 7 metabolites were isolated and identified in urine and 3 metabolites in feces. About 75% of the urinary and fecal radioactive metabolites were unconjugated. Urinary excretion of methadone and its major N-monomethylated metabolite accounted for 17% to 57% of the given dose. The ratio of metabolite to parent drug increased in 5 of 6 subjects, and the urinary recovery of unchanged methadone decreased during the period. The results indicate that enhanced demethylation of methadone may occur during oral administration to man.

MeSH terms

  • Adult
  • Carbon Radioisotopes
  • Chromatography, Gas
  • Dealkylation
  • Feces / analysis
  • Female
  • Heroin Dependence / rehabilitation*
  • Humans
  • Hydroxylation
  • Male
  • Methadone / metabolism*
  • Methadone / therapeutic use
  • Methadone / urine
  • Oxides / urine
  • Time Factors

Substances

  • Carbon Radioisotopes
  • Oxides
  • Methadone