Overview
Sildenafil is a prescription medication in the class of phosphodiesterase type 5 (PDE5) inhibitors. It is widely known for treating erectile dysfunction and is also available in formulations for pulmonary arterial hypertension. Sildenafil relaxes vascular smooth muscle to increase blood flow in targeted tissues; it does not directly increase sexual desire and therefore is not an aphrodisiac in the usual sense.

How it works

Sildenafil inhibits the PDE5 enzyme, which normally breaks down cyclic guanosine monophosphate (cGMP) in smooth muscle cells. When cGMP levels remain elevated during sexual stimulation, smooth muscle relaxation in penile tissue allows increased blood inflow to the corpora cavernosa, facilitating erection. In the pulmonary circulation, similar vasodilatory effects reduce pulmonary vascular resistance and can improve symptoms of pulmonary arterial hypertension. Effects typically begin within about 30–60 minutes after oral dosing and may last for several hours depending on individual factors.

Medical uses

  • Treatment of erectile dysfunction in men, improving the ability to achieve and maintain an erection adequate for sexual activity when sexually stimulated.
  • Management of pulmonary arterial hypertension (PAH) under specific formulations and dosing regimens, where it helps lower pulmonary artery pressure and improve exercise capacity in some patients.
  • Research and off-label uses: clinicians and researchers have investigated PDE5 inhibitors in other conditions such as certain circulatory and endothelial disorders, but evidence varies by indication.

Safety, side effects and interactions

Common side effects include headache, flushing, nasal congestion, indigestion and transient visual changes. Serious but less common risks include a marked drop in blood pressure, priapism (a prolonged, painful erection requiring urgent care), and cardiovascular events in people with significant underlying heart disease. Sildenafil must not be taken with organic nitrates (for example, nitroglycerin) because the combination can produce a dangerous fall in blood pressure. Caution is required when combining sildenafil with alpha-blockers or other antihypertensive drugs, and dose adjustments or monitoring may be necessary.

Special populations and precautions

People with severe cardiovascular disease, recent stroke or myocardial infarction, severe hypotension, or certain hereditary eye conditions should avoid or use sildenafil only under specialist advice. Liver and kidney impairment can affect drug metabolism and clearance, and clinicians often tailor treatment accordingly. Use in women and in pregnancy has limited indications and requires specialist oversight; sildenafil is not a contraceptive and does not prevent sexually transmitted infections.

History and brand names

Sildenafil was discovered during research on treatments for angina, and its effect on erectile function emerged during clinical trials. It was developed and brought to market in the 1990s, transforming approaches to erectile dysfunction. It is marketed under several brand names worldwide; one well-known brand is commonly associated with the compound, while other brands and formulations are used for pulmonary hypertension and in different regions. Generic versions are widely available in many countries.

Practical considerations

Healthcare professionals assess cardiovascular risk and drug interactions before prescribing sildenafil. Patients are advised to follow the prescribed timing and not to exceed recommended dosing. If an erection lasts longer than four hours or there are severe or persistent adverse effects, urgent medical attention is required. Sildenafil does not affect fertility, and it does not serve as protection against sexually transmitted infections; safe-sex practices remain important.

Further resources