Human metabolism of antipyrine labelled with 14C in the pyrazolone ring or in the N-methyl group.
After ingestion of [N-14CH3]antipyrine by two healthy male subjects, the urinary recoveries of radioactivity plus norantipyrine (non-radioactive) were 63 and 73%. After ingestion of [3-14C]antipyrine in the same two subjects, the urinary recoveries of radioactivity were 84 and 99%. Therefore, N-demethylated metabolites which have not been identified before, besides norantipyrine, must account for 21--26% of the dose. Serum half-lives of total 14C were about 50% greater than those of unchanged antipyrine. The difference was less in the saliva. Three major metabolites of antipyrine, norantipyrine, 4-hydroxyantipyrine and 3-hydroxymethylantipyrine, in urine were determined by radio-t.l.c. and g.l.c. These three metabolites and antipyrine accounted for 50--69% of the administered dose. The urinary excretion half-lives of these three metabolites were similar to each other and to the serum half-life of antipyrine. 3-Hydroxymethylantipyrine in one subject was excreted more slowly than the other metabolites. The radioactive metabolite not extracted from urine by organic solvents was very polar, as judged by t.l.c.
D000328:Adult; D000983:Antipyrine / Q000378:metabolism*; D001711:Biotransformation; D002250:Carbon Radioisotopes; D003640:Dealkylation; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged
D002250:Carbon Radioisotopes; D000983:Antipyrine