Sildenafil: What it does, how to use it, and how to stay safe

Sildenafil is the active drug in Viagra and some generic products like Kamagra. People use it mainly for erectile dysfunction (ED) and, in a different form and dose, for pulmonary arterial hypertension (PAH). This page gives simple, practical facts so you can talk with your doctor and avoid common risks.

How sildenafil works and common dosing

Sildenafil relaxes blood vessels so blood flows easier to the penis or lungs, depending on the dose and formulation. For ED, typical tablets come in 25 mg, 50 mg, and 100 mg. Most people take one dose about 30–60 minutes before sex. It often works for up to 4–5 hours but doesn’t create automatic erections — sexual stimulation is still needed.

For PAH (sold as Revatio), sildenafil is usually given as 20 mg three times a day. That schedule is different from ED dosing, so don’t swap doses without medical advice. If you’re older, have liver problems, or take certain medicines, your prescriber may start at a lower dose.

Safety, side effects, and buying tips

Common side effects include headache, flushing, indigestion, nasal congestion, and mild visual changes (like a blue tint). Serious but rare issues are sudden vision loss, sudden hearing loss, or prolonged erections longer than 4 hours (priapism). If any of these happen, get emergency care.

Never combine sildenafil with nitrates (nitroglycerin or similar) — that can cause a dangerous drop in blood pressure. Tell your doctor about alpha-blockers, some blood pressure meds, certain antifungals and antibiotics, and grapefruit juice — these can change how sildenafil works. Always review your current medications with a clinician.

Buying online? Use caution. Get a prescription first and choose pharmacies you can verify. Read our posts on online pharmacy safety and honest reviews before ordering. Cheap pills from unknown sites may be counterfeit or unsafe. Discount services like GoodRx or pharmacy comparison guides can help you save but check legitimacy and shipping rules in your region.

Not responding to sildenafil? Other FDA-approved options include tadalafil (longer lasting), vardenafil, and avanafil. There are also non-pill routes and devices. If side effects or cost are a problem, talk to your provider about alternatives and dosing changes.

Want more practical reads? We have guides on Kamagra oral jelly, comparisons of ED alternatives, and tips for vetting online pharmacies. Read those if you plan to buy online or want a deeper look at options beyond sildenafil.

Final practical tip: don’t self-medicate. Get a medical check-up, discuss heart health and interactions, and use a verified pharmacy. That keeps treatment effective and reduces risk.