Abstract
Following the intravenous administration of anesthetic doses of thiopental, the distribution of the drug has been determined in blood, brain, liver, and fat of the rat and in the fat of dogs and human subjects. The in vivo rate of metabolism of this drug has been determined in normal rats and in subtotally hepatectomized or bilaterally nephrectomized rats.
In the rat, drug equilibrium occurs between blood, brain, and liver within one minute but not between blood and fat until one to two hours. At the time equilibrium is attained, the tissue/blood ratios are approximately 0.6, 2.5, and 7.0, respectively, for brain, liver, and fat. Maximum localization of the drug in human adipose tissue occurs within 1½ to 2½ hours, but not until about 4 hours in the dog. Once equilibrium has been established between blood and adipose tissue, thiopental appears to be mobilized from fat slightly faster in the rat than in the dog.
The rate of metabolism of thiopental in vivo in the rat during the first 6 hours after administration of the drug is approximately 10 per cent pen hour. In 12 hours approximately 90 per cent of the drug is metabolized. During the same period subtotally hepatectomized (70 per cent of the liver removed) and bilaterally nephrectomized animals metabolize only 27 per cent and 58 per cent of the drug, respectively.
Footnotes
- Received October 23, 1952.
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