Metabolism of cis-delta4-15(S)-15-methylprostaglandin F1alpha methyl ester in the rat.

The metabolic transformation and excretion of tritium-labeled cis-delta4-15(S)-15-methylprostaglandin F1alpha methyl ester (1) have been investigated in rats after chronic and single dose oral administration. Three metabolites have been identified from a partially purified urinary extract. They were the cis-delta4-15-methylprostaglandin F1alpha (2), 15-methyl-2,3-dinorprostaglandin F1alpha (3), and 15-methyl-2,3,4,5-tetranorprostaglandin F1alpha (4). The excretion of the drug-related species was significantly slower than that of the natural prostaglandin F2alpha. The slow excretion rate and the presence of unchanged cis-delta4-15-methylprostaglandin F1alpha in urine suggested that the metabolically protected prostaglandin could persist in the body and, therefore, exhibit longer duration of action.