What Is Sildenafil?
Sildenafil (commonly known by the brand name Viagra) is a medication used to treat erectile dysfunction (ED) in men. It is one of the most well-studied and widely used medications in the world, with decades of safety data. Beyond its well-known use for sexual function, sildenafil also has FDA approval for treating pulmonary arterial hypertension (high blood pressure in the lungs), and emerging research suggests it may have cardiovascular and longevity-related benefits.
How Does It Work?
Sildenafil belongs to a class of medications called PDE5 inhibitors (phosphodiesterase type 5 inhibitors). It works by blocking an enzyme (PDE5) that breaks down a chemical called cGMP. When cGMP levels rise, the smooth muscle in blood vessel walls relaxes, allowing blood vessels to dilate (widen). In the penis, this improved blood flow makes it easier to achieve and maintain an erection when sexually aroused. Importantly, sildenafil requires sexual stimulation to work — it does not cause an erection on its own.
Benefits
- Treats erectile dysfunction — helps men with ED achieve and maintain erections sufficient for sexual activity
- Improves sexual confidence and wellbeing — effective for a wide range of ED causes, including vascular, age-related, and stress-related
- Cardiovascular benefits — emerging research suggests sildenafil may support vascular health and have cardioprotective effects
- Blood flow improvement — vasodilatory effects extend beyond the genitals, supporting healthy circulation
- Potential longevity benefits — observational studies suggest sildenafil users may have reduced rates of cardiovascular disease and Alzheimer's disease (research is ongoing)
- Well-established safety profile — decades of clinical use with extensive safety data
How to Take Sildenafil
- Form: Oral tablet
- Standard dose for ED: 25–100 mg taken as needed, approximately 30–60 minutes before sexual activity
- Common starting dose: 50 mg
- Maximum dose: 100 mg per day — do not exceed this
- Frequency: Not more than once per 24-hour period
- With or without food: Can be taken either way; however, a high-fat meal may slow absorption and delay onset of action
- Duration of effect: Typically 4–6 hours
- Low-dose daily use: Some men use a lower daily dose (typically 25 mg daily) as part of a cardiovascular or longevity protocol — your provider will advise if this is appropriate for you
What to Expect
- Within 30–60 minutes: Sildenafil begins to take effect; onset can be faster on an empty stomach
- Sexual stimulation is required — sildenafil enhances the body's natural erectile response but does not cause erections without arousal
- 4–6 hours: Duration of action; effects wear off gradually
Side Effects
Sildenafil is generally well tolerated. Common side effects are usually mild and temporary:
- Headache — most common side effect, related to blood vessel dilation
- Flushing or warmth
- Stuffy or runny nose
- Indigestion or upset stomach
- Visual changes — temporary changes in color vision (bluish tint) or light sensitivity; uncommon but possible
- Dizziness
- Low blood pressure — especially if combined with other blood pressure medications or alcohol
Serious side effect — seek immediate medical attention:
- Priapism — a prolonged, painful erection lasting more than 4 hours; this is a medical emergency requiring immediate treatment
- Sudden vision or hearing loss — rare but serious; stop the medication and seek care immediately
- Severe low blood pressure — especially if combined with nitrate medications
Who Should Not Take Sildenafil?
- Anyone taking nitrate medications (such as nitroglycerin, isosorbide mononitrate or dinitrate) — this combination can cause a dangerous drop in blood pressure. This is an absolute contraindication.
- People with severe heart disease or who have recently had a heart attack or stroke
- People with very low blood pressure (hypotension)
- People with severe liver disease
- People with retinitis pigmentosa (a rare eye condition)
- Anyone with known allergy to sildenafil
Storage Instructions
- Store at room temperature (59°F–86°F / 15°C–30°C)
- Keep away from moisture and heat
- Keep out of reach of children
Frequently Asked Questions
How long does sildenafil last?
The effects of sildenafil typically last 4–6 hours. During this window, achieving and maintaining an erection with sexual stimulation should be easier. The medication gradually wears off after this time.
Do I need to take sildenafil every day?
Sildenafil can be taken as needed (before sexual activity) or, in some protocols, at a low daily dose for cardiovascular or longevity purposes. Your provider will recommend the best approach for your situation.
What if sildenafil doesn't work for me?
Sildenafil works best when sexual stimulation is present. If it is not working, consider: taking it on an empty stomach, waiting the full 60 minutes before activity, or discussing a dose adjustment with your provider. Sometimes a different PDE5 inhibitor (like tadalafil) may work better for some individuals.
Can I drink alcohol while taking sildenafil?
Moderate alcohol is generally acceptable, but excessive alcohol can interfere with achieving an erection and increase the risk of side effects like dizziness or low blood pressure. Limit alcohol use when taking sildenafil.
Are there cardiovascular benefits to sildenafil beyond ED?
Emerging research is quite promising. Large observational studies have found that regular sildenafil use is associated with lower rates of cardiovascular events and, intriguingly, reduced risk of Alzheimer's disease. The mechanisms likely relate to its vasodilatory and anti-inflammatory effects. Clinical trials are ongoing to better understand these potential benefits.