Metabolic fate of rioprostil in the rat--in vivo and in liver perfusion.

The metabolic fate of rioprostil is investigated in the rat--in vivo and in liver perfusions--using the tritriated drug. Seven metabolites are isolated from the perfusion model and identified by 1H-NMR spectroscopy, mass spectrometry (EI/CI/FAB) and combined GC-MS (EI/CI). Rioprostil is extensively metabolized. The main metabolite in urine (81.2%) and bile (50.1%) is the tetranor-1,16-dicarboxylic acid. The tetranor carboxylic acid is isolated in smaller amounts (8.1 and 18.2% resp.). Rioprostil itself can be detected neither in the urine nor in the bile of the in vivo studies. Thus, the metabolism of rioprostil proceeds via the biotransformation pathways of the naturally occurring prostaglandins.