THE FATE AND EXCRETION OF C¹⁴-LABELED PENTYLENETETRAZOL IN THE RAT, WITH COMMENTS ON ANALYTICAL METHODS FOR PENTYLENETETRAZOL

¹ Department of Pharmacology, University of Utah College of Medicine, Salt Lake City, Utah

In the rat, Metrazol is metabolized to an inactive compound. The halftime of disappearance of biologically-active Metrazol is about 23 hours. Partial hepatectomy prolongs the sojourn of active Metrazol in the body; nephrectomy is without effect.

Following intravenous injection of radioactive Metrazol, radioactive material is excreted largely in the urine and to a slight extent in the feces. The urinary excretion is prolonged; 50 per cent of the injected Metrazol is accounted for in urine collected over 12 hours and 75 per cent in urine collected over 48 hours following injection. The rate of urinary excretion of radioactive material reaches a peak 3 hours after injection. The curve for rate of excretion closely parallels the curve representing blood concentration of changed Metrazol.

Only a single radioactive compound, chromatographically indistinguishable from Metrazol, has been found in either urine or feces. Extracts of rat urine have yielded a compound which produces typical Metrazol seizures in mice. Additional chemical studies suggest that this compound is Metrazol. It appears that the changed Metrazol, presumed to be excreted, reverts to Metrazol either in urine or in the process of identification.

The influence of time, temperature and quantity of Metrazol on losses due to sublimation and evaporation of the compound has been studied. When working with small amounts of Metrazol, the losses with ordinary extraction procedures may be a major fraction of the drug present.

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