Discontinue use if any sudden visual defects occur. Not recommended in other forms of pulmonary arterial HTN, patients w/ known hereditary degenerative retinal disorders eg, retinitis pigmentosa. Not to be used in patients w/ pulmonary HTN secondary to sickle cell anaemia. Anatomical penis deformation eg, angulation, cavernosal fibrosis or Peyronie's disease, or conditions predisposing to priapism eg, sickle cell anaemia, multiple myeloma or leukemia. Pulmonary arterial HTN class I & IV; non-arteritic anterior ischaemic optic neuropathy; hypotension, fluid depletion, severe left ventricular outflow obstruction or autonomic dysfunction; bleeding disorders or active peptic ulceration; pulmonary HTN associated w/ pulmonary veno-occlusive disease; hearing impairment. Serious CV events in male erectile dysfunction eg, MI, unstable angina, sudden cardiac death, ventricular arrhythmia, cerebrovascular haemorrhage, transient ischaemic attack, HTN & hypotension. Concomitant use w/ α-blockers, vit K antagonist, bosentan & other PDE-5 inhibitors. Galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption. May affect ability to drive & use machines. Not recommended in women of childbearing potential. Not to be used during pregnancy. Lactation. Not recommended in childn <18 yr.