Analytical Methods for [3H]-Enisoprost, an Anti-Secretory PGE1 Analogue, and its Metabolites

This article describes analytical methods developed to study the disposition of [3 H]enisoprost, a PGE1 analogue, in man. Solid-phase extraction and HPLRC* were used. These methods were scaled up to allow isolation and purification of urinary metabolites. These were identified by GC-MS of their ME-MO-TMS and PFB-MO-TMS derivatives. The latter provided mol. wt. data from the intense [M-PFB]- ions formed by NCI with ammonia, and the former provided information on sites of metabolism from the characteristic EI fragmentation pathways. The addition of a cholinesterase inhibitor, 2 M pyridostigmine bromide, served to stabilize enisoprost in whole blood immediately after collection; in its absence enisoprost was rapidly degraded to its carboxylic acid metabolite (SC-36067).