Sildenafil: What It Does, How to Use It Safely

Sildenafil is a medicine most people know as Viagra. It relaxes blood vessels so blood flows more easily. Doctors prescribe it for erectile dysfunction and for pulmonary arterial hypertension under different doses. Knowing how it works and how to take it keeps you safer and helps it work better.

Take sildenafil 30–60 minutes before sex. For erectile dysfunction, common doses are 25 mg, 50 mg, or 100 mg. Start with a lower dose if you’re older, have health conditions, or take other medicines. Food—especially a heavy, high-fat meal—can slow how fast it works. Alcohol can reduce response and raise the chance of dizziness.

Side effects and when to stop

Common side effects include headache, flushing, nasal congestion, and upset stomach. Less common but serious effects are chest pain, sudden vision changes, or an erection lasting more than four hours (priapism). Stop taking it and get medical help if you have chest pain, sudden vision loss, or an erection that won’t go away. These are rare but need urgent care.

Interactions and safety

Do not take sildenafil with nitrates (nitroglycerin) or with riociguat. Mixing these can cause a dangerous drop in blood pressure. Tell your doctor about heart disease, low blood pressure, liver or kidney problems, and any eye disease. Some medicines — like certain HIV protease inhibitors, antifungals, and antibiotics — change sildenafil levels. Your doctor may adjust your dose.

Sildenafil works differently when used for lung problems. For pulmonary arterial hypertension, lower daily doses are used and the goal is to improve blood flow in the lungs, reduce shortness of breath, and improve exercise capacity. Follow the prescription and regular checkups closely.

Want alternatives? Tadalafil and vardenafil work similarly but have different timing and side effects. Tadalafil lasts longer and can be taken daily at low dose. If sildenafil doesn’t work or causes bad side effects, talk with your prescriber about switching or adjusting dose.

Buying sildenafil online requires caution. Use pharmacies that require a prescription, show clear contact info, and have proper credentials. Avoid sites that promise cheap pills without asking medical questions. Counterfeit erectile dysfunction drugs are common and can be dangerous.

Practical tips: try a lower dose first, avoid heavy meals before sex, don’t mix with nitrates or excessive alcohol, and track side effects. If you have frequent erections lasting hours, sudden vision or hearing changes, or fainting, seek emergency care. For everyday concerns, book an appointment to review medications and heart health before starting sildenafil.

One more thing: sildenafil can be effective and safe when used correctly and with medical guidance. Talk openly with your clinician about goals, risks, and real-life expectations—so you get benefits without surprises.

If cost is a concern, ask about generic sildenafil and patient assistance programs. Generic versions work the same at lower price. Keep an up-to-date list of your medicines and share it with the prescriber. That simple step prevents bad drug interactions and keeps treatment working well. Ask your pharmacist.