What is the use of Sildenafil (Viagra)?

From the Guidelines

Sildenafil is recommended as a first-line treatment for erectile dysfunction, with a typical dose of 50mg taken approximately one hour before sexual activity, unless contraindicated 1.

Key Points

• Sildenafil works by inhibiting phosphodiesterase type 5 (PDE5), an enzyme that breaks down cyclic guanosine monophosphate (cGMP), promoting smooth muscle relaxation in the penis and increasing blood flow 1.
• The medication should not be taken with nitrates, such as nitroglycerin, as this combination can cause dangerous drops in blood pressure 1.
• Patients with certain cardiovascular conditions, severe liver or kidney disease, or recent stroke or heart attack should use sildenafil cautiously or avoid it altogether 1.
• Common side effects include headache, flushing, indigestion, nasal congestion, and visual disturbances 1.
• Sildenafil typically works for about 4-5 hours, though its effects may last longer in some individuals 1.

Considerations

• The choice of sildenafil as a treatment for erectile dysfunction should be based on individual patient preferences, including ease of use, cost of medication, and adverse effects profile 1.
• Sildenafil has been shown to be effective in improving erectile function and frequency of penile penetration or erection maintenance, compared to placebo 1.
• The medication can be combined with other ED therapies, such as psychotherapy, dihydroergotamine, cabergoline, atorvastatin, quinapril, and alfuzosin, for greater improvements in erectile function and frequency of penile penetration or maintenance of erection 1.

From the FDA Drug Label

Sildenafil tablets are indicated for the treatment of pulmonary arterial hypertension (WHO Group I) in adults to improve exercise ability and delay clinical worsening. The efficacy of sildenafil tablets in the treatment of pulmonary arterial hypertension (PAH) has not been adequately evaluated in patients taking bosentan. Sildenafil tablets are a prescription medicine used in adults to treat pulmonary arterial hypertension (PAH). It is not known if sildenafil tablets are effective for the treatment of PAH in people who are also taking a medicine called bosentan (Tracleer®)

The main use of sildenafil is for the treatment of pulmonary arterial hypertension (PAH) in adults to improve exercise ability and delay clinical worsening.

• The efficacy of sildenafil in patients taking bosentan has not been adequately evaluated.
• Sildenafil is not for use in children.
• Contraindications include taking nitrate medicines and being allergic to sildenafil.
• Patients should be advised to seek immediate medical attention for a sudden loss of vision or hearing while taking sildenafil tablets 2 2

From the Research

Sildenafil Overview

• Sildenafil is an oral therapy for erectile dysfunction of a broad range of causes, working by selectively inhibiting phosphodiesterase type 5 3.
• It allows corpus cavernosum smooth muscle to relax, potentiating erections during sexual stimulation 3.
• Sildenafil is rapidly absorbed, with dose-proportional peak plasma concentrations within 1 hour of administration, and an elimination half-life of 3 to 5 hours 3.

Efficacy and Safety

• Sildenafil was associated with dose-related improvements in the frequency, hardness, and duration of erections, and in patients' abilities to achieve and maintain erections adequate for successful sexual intercourse 3.
• The efficacy of sildenafil was not affected by patient age or by antihypertensive or antidepressant medications 3.
• Sildenafil is an effective and well-tolerated treatment for erectile dysfunction regardless of patient age, including men at least 75 years old 4.
• Common adverse events associated with sildenafil were transient and mild or moderate, and included headache, flushing, dyspepsia, nasal congestion, and abnormal vision 3.

Dosage and Administration

• Dosages usually begin at 50mg taken when needed, at least 1 hour before sexual activity, no more than once daily 3.
• The maximum dose is 100mg when needed once daily, and lower doses (e.g., 25mg) may be used in elderly patients and those with hepatic or renal impairment or receiving cytochrome P450 enzyme CYP3A4 inhibitors 3.
• Regular use of sildenafil has a therapeutic effect similar to that of tadalafil but better than that of sildenafil on-demand, without more adverse effects 5.

Cardiovascular Effects

• PDE-5 inhibitors, including sildenafil, have cardiovascular effects, inhibiting PDE-5 enzymes in pulmonary vasculature, causing vasodilation that decreases pulmonary vascular pressure 6.
• Sildenafil is approved for treatment of patients with pulmonary hypertension, and improves cardiac output by balancing pulmonary and systemic vasodilation 6.
• PDE-5 inhibition with sildenafil may have beneficial effects in conditions such as myocardial infarction and endothelial dysfunction 6.