Urinary excretion of methadone in man

Abstract

The renal elimination of methadone and its mafor metabolite by subfects on a methadone maintenance program was studied quantitatively. The concentrations of unchanged drug and metabolite in random urine samples were dose dependent. Urinary excretion was found to constitute the mafor excretory pathway at daily doses in excess of 55 mg. Excretion of methadone was markedly enhanced by acidification of the urine, while the metabolite was less affected by changes in urine pH. A sex difference in the pattern of excretion of methadone and its metabolite was found; it may be related to the rate of biotransformation of the drug.