Metabolism of synthetic surfactants

This article provided a brief overview of synthetic surfactants and DPPC metabolism, and summarized disposition data on the most widely used synthetic surfactant, CPHT (colfosceril palmitate, hexadecanol, and tyloxapol; Exosurf Neonatal, Burroughs Wellcome Co.). In separate experiments, young male rabbits were given intratracheal administrations of CPHT trace-labeled with either hexadecanol-3-[14C], choline-labeled [14C]DPPC, or [3H]tyloxapol. In mass balance and tissue distribution studies, radioactivity was quantitated in excreta and selected tissues over 5 days. Hexadecanol entered the pathways of intermediary lipid metabolism, via oxidation to palmitic acid, which was then utilized in the synthesis of phospholipids. After 5 days, most of the radiolabeled dose (56%) was distributed throughout the body, with renal (4%) and fecal (2%) excretion being minor routes of elimination compared with expired air (28%). The active component, DPPC, was still retained by the body (72%) after 5 days, having entered the pathways of lipid metabolism to become tissue associated. At this time, the lung and liver each contained approximately 10% of the labeled dose, whereas elimination in excreta (8%) was minimal compared with that in expired air (17%). Tyloxapol and metabolites were retained by the lung, released slowly (t1/2 = 5 to 6 days) into the systemic circulation, and eliminated through fecal (27%) and renal (26%) excretion.