METABOLISM OF S³⁵ THIOPENTAL (PENTOTHAL)

Chemical and Paper Chromatographic Studies of S³⁵ Excretion by the Rat and Monkey

¹ Abbott Laboratories, North Chicago, Illinois

1 . Pentothal labeled with S³⁵ has been synthesized and the excretion of S³⁵ has been studied in the rat and the monkey.

2. At the end of four days an average of 89.5 per cent of the radioactivity was accounted for in the rat after an intraperitoneal injection of 40 mgm./kgm. of S³⁵-Pentothal. Of the total radioactivity injected, 7.3 per cent was excreted by the kidney as chloroform extractable material, 26.7 per cent as inorganic sulfate, 7.7 per cent as acid hydrolyzable sulfate, and 40.1 per cent as unclassified sulfur. Only 5.3 per cent was excreted in the feces and 2 per cent in the carcass.

3. At the end of four days a monkey injected intravenously with 35 mgm./kgm. excreted 86.2 per cent of the radioactivity in the urine with 14.1 per cent as chloroform extractable material and 17.1 per cent as inorganic sulfate.

4. A maximum of 2.8 per cent of the radioactivity was excreted as thiourea in twenty-four hours in the rat.

5. Paper chromatography of the urine of the monkey indicated the presence of at least twelve radioactive compounds.