Isolation and characterization of the urinary metabolites of arbaprostil in the male dog after intravenous administration.

The profile of urinary metabolites of 3H-arbaprostil was characterized in the male dog after intravenous administration. The major metabolites were purified and their structures deduced by gas chromatography/mass spectrometry (GC/MS) studies after conversion to the methyl ester-methoxime-trimethylsilyl ether derivatives, aided by GC with simultaneous radioactivity monitoring. The identified metabolites accounted for 96% of the urinary excretion products. beta-Oxidation of the carboxy side-chain of arbaprostil to 15-methyl-2,3,4,5-tetranor PGE1, via the 15-methyl-2,3-dinor PGE2 intermediate, appeared to be the most significant metabolic pathway. In contrast to the rat, the following were observed in the dog: glucuronic acid conjugation of the 15-methyl-2,3,4,5-tetranor PGE, and PGA metabolites; detection of the 15-methyl-2,3-dinor PGE2 intermediate; absence of 19-hydroxyl-15-methyl-2,3,4,5-tetranor PGA, and PGB metabolites; oxidation at C-20; and excretion of some parent drug.