The Fate of Radioactive Morphine in Man

Recently very important contributions on the fate of analgesics have been made by the Department of Pharmacology and Experimental Therapeutics of the University of California in San Francisco. Among their important papers is the study, by Elliott, Tolbert, Adler, and Anderson (99), of morphine labeled with in the iV-methyl group. 

Urinary excretion during the first 6 hr. accounted for 29-74 % of the injected morphine, and for 56-91 % at 24 hr. (see Table 5). Three of the 5 subjects excreted 5-7 % during the 2nd day and all excreted small amounts the 3rd day. The addict excreted morphine at the most rapid rate and had the greatest urine output. Nontolerant subjects excreted 7-10% of the dose in the feces in 3-4 days. In contrast, the feces of the addict contained only a negligible amount of radioactivity. 

Vomitus from subject AC at 6 00 contained 0.5 % of injected dose. Duodenal tube samples from subject AC contained the highest concentration of activity at 6 hr. and were about half as active at 24 hr. 

All subjects excreted 4-6% of injected radioactivity in the expired air during the first 24 hr. This was in contrast to rats where the females excreted very little C by this route. In man the peak rate of respiratory excretion was during the 2nd hr., and fell to low levels at 6-8 hrs. However, measurable levels of radioactivity were present in the expired air of 2 subjects for 4-5 days. 

Low recoveries in subjects AC, HB, and PR were not believed to be due to technique. Possibly there may have been fixation and slow hberation or excretion by some other route such as sweat (99). 

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