In vivo metabolism of the leukotriene receptor antagonist, 5-(2-dodecylphenyl)-4,6-dithianonanedioic acid (SK & F 102,081) in the guinea pig

Both leukotrienes and their receptor antagonists possess substantial pharmacologic activity in in vitro systems, but their duration of action in vivo is extremely short. The exact mechanism of rapid inactivation of these lipids is unknown, but is likely due to metabolism. Therefore, the metabolic fate of a model antagonist 5-(2-dodecylphenyl)-4,6-dithianonanedioic acid (SK&F 102,081) was elucidated in anesthetized guinea pigs. Following iv administration of [14C]SK&F 102,081 (5 mg/kg), 85% of injected radioactivity was excreted in bile in 1 hr. Approximately 6% of the radioactivity in bile was associated with parent. At least 14 metabolites were present in bile, 2 of which accounted for almost 60% of the excreted radioactivity. Identification of biliary metabolites revealed that metabolism occurred by two major routes, omega-oxidation with subsequent beta-oxidation and acyl glucuronidation at approximately a 4:1 ratio. Since current structure-activity relationships suggest that omega-oxidation results in the loss of pharmacologic activity of SK&F 102,081, the rapid loss in pharmacologic activity observed in vivo may be due to rapid metabolism.