Excretion of Carbon-14 by Man after Administration of Morphine-N-Methyl-C 14 ∗

Abstract

Summary

1. Therapeutic doses of morphine-N-methyl-C¹⁴ have been administered to 5 human subjects. The major portion of the radioactivity is excreted in 24 hours. Urinary excretion accounted for most of the recovered activity, and there was some correlation between urine volumes and carbon-14 excretion when these volumes were abnormally high or low. 2. Fecal excretion accounted for 7 to 10% of the dose and the possibility that this material originates in the bile as “bound” morphine with subsequent hydrolysis in the intestine is discussed. Intestinal excretion is not as important in man as in rats. 3. Pulmonary excretion of C¹⁴O₂ ranged from 31/2 to 6% of the injected dose in 24 hours. There was no sex difference in excretion by this route, as has been observed in the rat. 4. The carbon-14 excretion pattern for the one addict was similar to the nontolerant subjects, except in the case of the feces. 5. It has been shown that it is feasible to do tracer studies in normal subjects using less than a microcurie of carbon-14.