Indicated for the treatment of pulmonary arterial hypertension. Pharmacokinetic data (moderately high molecular weight and high percentage of protein binding capacity) make it unlikely a milk passage in significant amounts.Low oral bioavailability hinders its passage from the ingested milk to infant's plasma, except in preterm and immediate neonatal period that may show an increased intestinal permeability. Although no samples have been taken to analyze the concentration in breast milk, a 30 weeks old premature infant who was breastfed for 2-and-a-half months, while his mother was treated with Bosentan and Sildenafil, did not present side-effects. It is approved for Pediatric use from 1-year-old or 10 kg to higher, but there are not published data on neonatal indication. It would be preferred a safer alternative until more data is available about this drug regarding breastfeeding, especially during the neonatal period and in case of prematurity.