Patients w/ WHO class I functional status of PAH. Elevations of liver aminotransferases. Monitor for signs of hepatic injury; monitor ALT & AST mthly. Decrease in Hb conc. Not recommended in patients w/ severe anaemia. Measure Hb conc prior to initiation of treatment & repeatedly during treatment as clinically indicated. Patients w/ pulmonary veno-occlusive disease. Avoid concomitant use w/ strong CYP3A4 inducers (eg, rifampicin, St. John's wort, carbamazepine & phenytoin). Exercise caution when administered concomitantly w/ strong CYP3A4 inhibitors (eg, itraconazole, ketoconazole, voriconazole, clarithromycin, telithromycin, nefazodone, ritonavir & saquinavir). Patients w/ renal impairment have higher risk of hypotension & anaemia. Rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption. Contains lecithin derived from soya. Minor influence on the ability to drive & use machines. Not recommended in patients w/ moderate hepatic impairment; patients undergoing dialysis. Should only be initiated in women of childbearing potential when absence of pregnancy has been verified. Women should not become pregnant for 1 mth after treatment discontinuation. Elderly >75 yr.