Sildenafil: what you need to know right now

Sildenafil is best known as Viagra, a drug that helps with erectile dysfunction (ED). It’s also used for some lung blood-pressure problems. If you’re thinking about using it, you probably want clear, useful facts — not medical jargon. Here’s a quick, practical guide to how it works, common doses, safety red flags, and smart tips for buying it online.

How sildenafil works and common uses

Sildenafil blocks an enzyme (PDE5) that narrows blood vessels. That lets more blood reach the penis during sexual arousal, helping you get and keep an erection. For ED, common doses are 25 mg, 50 mg, or 100 mg taken about 30–60 minutes before sex. Most people find its effect lasts around 4–6 hours, though that varies.

For pulmonary arterial hypertension (a lung condition), sildenafil is used differently and at different doses. Don’t copy ED dosing for other conditions — follow your doctor’s instruction.

Safety, side effects, and drug interactions

Typical side effects are headache, flushing, nasal congestion, upset stomach, and visual changes (like a blue tint). These are usually mild and short-lived. Stop and call a doctor if you have sudden vision or hearing loss, chest pain, fainting, or an erection lasting more than four hours (priapism). Those are medical emergencies.

Big interaction to remember: never take sildenafil with nitrates (often prescribed for chest pain). That combo can cause a dangerous drop in blood pressure. Also be careful with alpha blockers, some blood pressure meds, and strong CYP3A4 inhibitors (like ritonavir or some antifungals) — they can raise sildenafil levels and increase side effects. Grapefruit or grapefruit juice can also affect drug levels for some people.

If you have heart disease, recent stroke or heart attack, low blood pressure, or certain eye problems, talk to your doctor before using sildenafil. Your doctor can help pick a safe dose and decide whether the drug is right for you.

Want to buy sildenafil online? A few quick tips: only use licensed pharmacies that require a prescription, check for a real pharmacist contact, read recent independent reviews, and avoid prices that look too-good-to-be-true (those pills may be fake). If a site offers sildenafil without asking for any medical info, walk away. A short online consultation with a legitimate clinic or your own prescriber is the safer route.

Looking for alternatives or more detail? We have guides comparing ED options, exploring natural approaches, and showing safe ways to order meds online. Read those to weigh pros and cons before you decide. And if you’re unsure at any step, ask a clinician — a quick chat can prevent a lot of trouble.