Abstract
Based on the determination of radioactivity after a subcutaneous injection of C14-labeled methadone*·HBr into rats, it was found that gastric excretion does not play a significant role in the elimination of the drug. The accumulation of radioactivity in the stomach is a result of regurgitation from the small intestine. The presence of radioactivity in the small intestine itself is a result of the inflow of radioactive bile.
Radioactivity makes its appearance in the bile within ten minutes after a subcutaneous injection and becomes increasingly concentrated resulting in an increasing minute output as time progresses. As much as 17 per cent of an injected dose of 5 mgm./kgm. can be recovered from the bile during a period of three hours. An amount representing 1.5 per cent of a subcutaneous dose is readily reabsorbed from the small intestine within this period.
In one pregnant rat, considerable amounts of radioactivity were found in the fetuses and placentae.
Footnotes
- Received November 25, 1949.
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