Thorough medical history & physical examination should be undertaken to diagnose erectile dysfunction, determine potential underlying causes & identify appropriate treatment. Should not be used in men for whom sexual activity is inadvisable. Priapism. Co-administration of an α-blocker may lead to symptomatic hypotension. Patients w/ retinitis pigmentosa; bleeding disorders or active peptic ulceration; anatomical deformation of the penis (eg, angulation, cavernosal fibrosis or Peyronie's disease) or in patients who have conditions which may predispose them to priapism (eg, sickle cell anemia, multiple myeloma or leukemia); resting HTN (BP >170/110), life-threatening arrhythmia w/in the last 6 mth & history of cardiac failure or CAD causing unstable angina. Discontinue use if sudden decrease or loss of hearing occur. May affect ability to drive or operate machinery.