Patients w/ WHO class I functional status of PAH. Treatment may only be started if the systemic systolic BP is >85 mmHg. No effect on healing of existing digital ulcers. Increases in liver aminotransferases. Measure liver aminotransferase values before the start of treatment & then mthly throughout treatment. Discontinue in case of clinical symptoms associated w/ liver damage. Decrease in Hb conc. Check Hb conc prior to initiation of treatment, at mthly intervals during the 1st 4 mth of treatment then every 3 mth. Reports of sickle cell anaemia crises in patients who already had sickle cell anaemia before start of treatment. Patients w/ pulmonary veno-occlusive disease. Monitor patients for signs of fluid retention (eg, wt increase). HIV patients being treated w/ antiretroviral drugs. Perform mthly pregnancy tests during treatment to ensure that pregnancy is detected as early as possible. Breast-feeding mothers should wean their babies. Childn & adolescent.