Sildenafil — what it does, how to use it, and what to watch for

Sildenafil is a widely used medicine best known for treating erectile dysfunction (ED). It’s also prescribed for pulmonary arterial hypertension (PAH) under different brand names and doses. If you’re considering sildenafil, this page gives clear, practical info: how it works, common doses, side effects to expect, key drug interactions, and simple tips for safe online purchases.

How to take sildenafil

For ED, typical doses are 25 mg, 50 mg, or 100 mg taken about 30–60 minutes before sexual activity. Most people start at 50 mg and adjust with a doctor. Don’t take it more than once every 24 hours. For pulmonary hypertension (Revatio), the usual dose is 20 mg three times a day — that schedule is different, so follow your prescription closely.

Sildenafil works by relaxing blood vessels and increasing blood flow to certain areas. Its effect usually lasts around 4–6 hours, though that varies by person. Food, especially a heavy or high-fat meal, can slow how quickly it starts to work. Avoid mixing it with alcohol if you’re concerned about dizziness or low blood pressure.

Side effects, warnings, and interactions

Common side effects include headache, flushing, indigestion, nasal congestion, and sometimes mild vision changes (like blue tinting). Most side effects are short-lived, but watch for anything that lasts or gets worse.

Never take sildenafil with nitrates (found in some chest pain meds). That combo can cause a dangerous drop in blood pressure. Also be careful if you take alpha-blockers, certain antifungals, macrolide antibiotics, or HIV protease inhibitors — these can change sildenafil levels. If you’ve had a recent heart attack, stroke, or have very low blood pressure, talk to your doctor before using it.

Priapism (an erection lasting more than 4 hours) is rare but a medical emergency. Seek immediate care if it happens. If you notice sudden vision loss or sudden hearing problems after taking sildenafil, stop it and get medical help right away.

Looking for alternatives? Tadalafil (longer-lasting), vardenafil, and avanafil are other PDE5 inhibitors. Each has different onset time and duration, so discuss options with your prescriber to find what fits your lifestyle and health.

Final practical tip: always tell your doctor about other meds and health conditions. That keeps treatment safe and effective.

If you want, scroll the posts under this tag for related articles on buying meds online, safe pharmacy practices, and alternatives. And if you’re thinking about ordering online, read the safety tips below before you buy.

Note: This page is for general information and not a substitute for medical advice. Talk with your healthcare provider for recommendations tailored to you.