Abstract: Inhaled prostaglandin E1 (IPGE1) is a potential selective pulmonary vasodilator in neonatal pulmonary hypertension. The objective of this study was to evaluate the bioavailability and metabolism of IPGE1. Anesthetized ventilated piglets received either high dose IPGE1 (1200 ng/kg/min) [Study group] or nebulized saline [Control group] using a jet nebulizer. PGE1 and its metabolite, 15-keto-PGE1, were quantified in blood, urine and lung tissue using high performance liquid chromatography-mass spectrometry. Fourteen piglets underwent the experimental protocol (age 1-9 days). Of these, nine received IPGE1 and five received nebulized saline. Among control pigs, two died of complications at 3-4 h, one at 12-13 h and the remaining two were euthanized at 24 h after start of aerosol. In the study group, three animals died after 14-15 h of aerosol treatment of iatrogenic complications and six animals received aerosol for 24 h. Plasma and urine PGE1 levels increased significantly over time in study (p<0.05) but not control animals. Plasma and urinary 15-keto-PGE1 levels and lung tissue prostaglandin profile were comparable in study and control animals. In conclusion, this is the first report of the tissue distribution, metabolism and excretion of prolonged high dose IPGE1. The increase in PGE1 levels in plasma and urine over time without accumulation in lung tissue or systemic side effects suggests effective aerosol delivery, extensive pulmonary metabolism and efficient excretory mechanisms.