Patients should be diagnosed (i.e., medical history and physical examination) for erectile dysfunction and potential underlying causes determined before starting treatment with sildenafil.
There are no controlled clinical studies on the safety and efficacy of sildenafil in the following sub-groups of patients, and if prescribed, should be done with caution: Recent (within the last 6 months) myocardial infarction, stroke or life-threatening arrhythmia; Resting hypotension (<90/50 mmHg) or hypertension (>170/110 mmHg); Severe hepatic impairment; Severe renal impairment; Known hereditary degenerative retinal disorders such as retinitis pigmentosa; Sickle cell anemia or related anemias.
Cardiovascular: Sexual activity in men with cardiovascular disease is associated with cardiac risks such as increase in cardiac work, heart rate, blood pressure, and myocardial oxygen demand similarly produced with moderate exercise. Thus, assessment of cardiovascular and cerebrovascular status of patients is necessary before initiating any treatment for erectile dysfunction. Erectile dysfunction treatments are generally not recommended when sexual activity is inadvisable due to the patient's underlying cardiovascular status. Advice patients to refrain from further sexual activity when they experience related symptoms like angina pectoris, dizziness or nausea upon initiation of sexual activity.
Some patients, particularly those with underlying cardiovascular disease, may be adversely affected by sildenafil's vasodilatory activity, especially in combination with sexual activity. Inform patients of the risk of hypotension especially when patients are on multidrug regimen for hypertension.
Patients with increased susceptibility to vasodilators include those with: Left ventricular outflow obstruction (e.g., aortic stenosis, hypertrophic obstructive cardiomyopathy); Rare syndrome of multiple system atrophy manifesting as severely impaired autonomic control of blood pressure.
Use phosphodiesterase type 5 (PDE5) inhibitors, including sildenafil, with caution when given together with alpha-blockers. Sildenafil, other PDE5 inhibitors, and alpha-adrenergic blocking agents are vasodilators and an additive hypotensive effect may be anticipated. Concurrent use of these drug classes can lead to symptomatic hypotension (e.g., dizziness, lightheadedness, fainting) in some patients.
Consider the following before using sildenafil concurrently with alpha-blockers: Make sure that patients are stable on alpha-blocker therapy before starting sildenafil or other PDE5 inhibitors.
Initiate PDE5 inhibitors at the lowest dose in patients who are stable on alpha-blocker therapy.
In patients already taking a PDE5 inhibitor at the optimized dose, initiate alpha-blocker therapy at the lowest dose. When taking a PDE5 inhibitor, further lowering of blood pressure may result from stepwise increase in alpha-blocker dose.
Other factors, including intravascular volume depletion and other anti-hypertensive drugs may affect the safety of combined use of PDE5 inhibitors and alpha-blockers.
Hematologic: There is no information on the safety of sildenafil in patients with bleeding disorders or active peptic ulceration. Use sildenafil with caution in these patients.
Genitourinary: Use sildenafil with caution in patients with penile anatomical deformities that may make erections and/or sexual intercourse painful or difficult: e.g., angulation, Peyronie's disease (induration of the penile corpora cavernosa producing a fibrous chordee).
Sildenafil should be used with caution in patients with conditions that may predispose to priapism (painful erection exceeding 6 hours): e.g., sickle-cell anemia, multiple myeloma, leukemia.
Prolonged erections and priapism may occur with sildenafil use. Advise patients to seek immediate medical attention if an erection persists longer than 4 hours or is extremely painful. Priapism may lead to penile tissue damage and permanent loss of potency if not treated immediately.
There is no data on the safety and efficacy of sildenafil when used in combination with other agents for the treatment of erectile dysfunction and therefore is not recommended.
Ophthalmologic: Visual disturbances such as changes in blue/green color discrimination may occur in patients taking sildenafil, particularly at high doses. Do not exceed recommended dose and frequency.
Use sildenafil with caution in patients with retinitis pigmentosa (a retinal disorder which in some patients maybe accompanied by a genetic disorder of retinal phosphodiesterases).
Immediately stop sildenafil use and seek medical attention when sudden loss of vision in one or both eyes is experienced as this may be a sign of non-arteritic ischemic optic neuropathy (NAION) which may result in decreased vision or permanent vision loss. NAION has been reported rarely with the use of all PDE5 inhibitors although it cannot be determined whether it is directly associated with such drugs or to other factors.
The risk of NAION may be higher in patients who: Have low cup to disc ratio ("crowded disc"); Are over 50 years old; Have diabetes; Are hypertensive; Have coronary artery disease; Have hyperlipidemia; Smoke.
Sudden Decrease or Loss of Hearing: Stop taking PDE5 inhibitors, including sildenafil, and promptly seek medical attention when sudden decrease or loss of hearing occurs. Sudden decrease or loss of hearing, which may be accompanied by tinnitus and dizziness, have been temporally associated with PDE5 inhibitors, including sildenafil. Whether these events are related directly to PDE5 inhibitors, or to other factors, have not been determined.
Ability to Drive or Operate Machines: Sildenafil may cause visual abnormalities and dizziness.
Patients receiving sildenafil should be advised to take precautions while performing activities requiring mental alertness or physical coordination. It should be carefully considered whether it is advisable to drive or operate machinery under these circumstances.
Infants and Children: The efficacy and safety of sildenafil in patients younger than 18 years old have not been established. Sildenafil is not indicated for use in neonates and children.