Results of an investigation on the urinary excretion of
codeine and
morphine after oral ingestion of 1 mg.kg-1 b.w
codeine are reported. The investigation run on seven clinically healthy subjects showed: low digestive absorption of
codeine (# 20%); rapid biotransformation of
codeine into
morphine (first urines excreted after absorption); rapid disappearance of
codeine from urines (#30 hrs); persistence of
morphine alone (#68 hrs); rapid evolution of the
codeine/
morphine ratio (inversion of the ratio after #18 hrs); total elimination of
morphine which can be greater than for
codeine; very different half-life periods for
codeine and
morphine (5.1 and 13.6 hrs); no other
codeine metabolites (nor-
codeine and nor-
morphine); very high individual variations; one subject with low activity of
cytochrome P 450 dbl/buFL. Finally, in an epidemiological survey of drug addict behaviors and detection of
drug addiction, it seems very difficult, may be even illusory and hazardous, to try and justify
morphine found in urines (
morphine,
heroin,
codeine, codethyline,
pholcodine...) except in the very legitimate case where the ratio of urine concentrations of
codeine and
morphine is greater than one.