Discontinue treatment in case of sudden decrease or loss of hearing. Serious CV, cerebrovascular & vascular events, including MI, sudden cardiac death, ventricular arrhythmia & HTN. Cardiac failure or CAD causing unstable angina. Retinitis pigmentosa, anatomical deformation of penis, predisposition to priapism. Non-arteritic anterior ischemic optic neuropathy (NAION). Patients who have suffered MI, stroke, life-threatening arrhythmia w/in 6 mth; w/ resting hypotension (BP <90/50) or HTN (BP 170/110). Not to take >25 mg dose w/in 4 hr of taking an α-blocker. Concomitant use w/ ritonavir. Men w/ underlying CV status for whom sexual activity is inadvisable.