THE METABOLIC FATE OF 5-(1-CYCLOHEXEN-1-YL)-1,5-DIMETHYL BARBITURIC ACID (HEXOBARBITAL, EVIPAL) AND OF 5-(1-CYCLOHEXEN-1-YL)-5-METHYL BARBITURIC ACID ("NOR-EVIPAL")

¹ Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
² University of North Carolina, Chapel Hill, North Carolina
³ Bristol Laboratories, Syracuse, New York

5-(1-Cyclohexen-1-yl)-5-methyl barbituric acid ("nor-evipal") is excreted unchanged in the urine of dogs in 13 per cent yield. An additional 20 per cent is excreted in the form of a new substance ("keto-nor-evipal") in which the cyclohexenyl ring has been oxidized presumably to a cyclohexenonyl group.

After administration of 5-(1-cyclohexen-1-yl)-1,5-dimethyl barbituric acid (hexobarbital, Evipal) to dogs, only traces of unchanged material and of norevipal were present in the urine. Keto-nor-evipal was isolated in 5 to 6 per cent yield. Two additional products ("keto-evipal I" and "keto-evipal II") were isolated in small amounts. These appear to be isomeric cyclohexenonyl derivatives of Evipal.

These oxidized products are inactive as anesthetics.

Comparison of the amounts of the several products from Evipal with the amounts of those products from nor-Evipal shows that primary demethylation of Evipal occurs to an extent of only about 2 per cent and that primary oxidation of Evipal occurs to an extent of at least 8 per cent.

The fates of about 90 per cent of the Evipal and of about 70 per cent of the norevipal are still unknown.