Sildenafil — what it does, how to use it, and practical safety tips

Sildenafil (brand name Viagra, generic sildenafil) treats erectile dysfunction (ED) and certain cases of pulmonary arterial hypertension (PAH). It relaxes blood vessels by blocking the PDE5 enzyme so blood flows more easily. That’s the short version — here’s what you need to know to use it safely and get reliable results.

How sildenafil works and how to take it

For ED, common tablet doses are 25 mg, 50 mg and 100 mg. Many people start at 50 mg and adjust with a doctor’s help. Take sildenafil 30–60 minutes before sexual activity. Expect it to work for about 4 hours, though effects can vary. A heavy, high-fat meal slows absorption — take it on a lighter stomach for faster action.

For PAH, doctors use different dosing and sometimes different formulations (like Revatio). Don’t swap doses between uses without medical advice. If you have reduced liver or kidney function, you may need a lower dose.

Side effects, interactions and red flags

Common side effects are headache, flushing, upset stomach, nasal congestion and mild visual changes like a blue tint. Serious reactions are rare but real: sudden vision loss, hearing loss, chest pain, fainting or an erection lasting longer than four hours (priapism). If any of those happen, get urgent medical help.

Never take sildenafil with nitrates (often prescribed for chest pain). The combination can cause dangerously low blood pressure. Also be cautious with alpha-blockers, some HIV protease inhibitors, macrolide antibiotics and strong CYP3A4 inhibitors — these can raise sildenafil blood levels. Tell your clinician about every medicine you take, including supplements and recreational drugs.

Older adults and people with heart disease need a medical check before using sildenafil. If you have uncontrolled high blood pressure, recent stroke or major heart problems, don't self-prescribe.

Buying tips: always get a valid prescription. If you shop online, pick pharmacies with clear contact info, verified seals, and honest reviews. Avoid extremely cheap offers — counterfeit pills are common and risky. Check packaging, expiry dates and batch numbers when your order arrives.

If cost is an issue, ask your doctor about the generic sildenafil citrate; it's the same active drug at lower price. Some clinics offer supervised dose trials so you can test how it works for you under medical guidance.

Final quick checklist: start at a sensible dose, avoid nitrates, skip heavy meals before taking it, watch for side effects, and only buy from trusted sources with a prescription. If sildenafil doesn’t work or causes trouble, talk to your doctor — there are other ED treatments and approaches that might fit better.