Sildenafil — what it does, how to use it, and how to stay safe

Sildenafil (brand name Viagra) can help with erectile dysfunction fast — usually working 30–60 minutes after a dose and lasting about 3–5 hours. That’s why many people choose it when they need a reliable, short-term option. But it’s not just a quick fix: knowing the right dose, risks, and how to buy real medicine matters.

How sildenafil works and common dosing

Sildenafil relaxes blood vessels in the penis so blood flow increases during sexual arousal. Typical adult dosing starts at 50 mg taken as needed about an hour before sex. Doctors often adjust between 25 mg and 100 mg based on effect and side effects. Don’t take it more than once every 24 hours.

If you’re older, on certain other meds, or have liver or kidney issues, your prescriber may suggest a lower starting dose. If you’re unsure, ask a clinician — that quick check can prevent bad interactions.

Side effects, risks, and red flags

Most side effects are mild: headache, flushing, nasal congestion, upset stomach, or temporary changes in vision (like a blue tint). Serious but rare issues include a painful erection lasting more than 4 hours (priapism) or sudden hearing/vision loss — these need immediate medical attention.

The biggest danger is mixing sildenafil with nitrates (nitroglycerin, some chest pain meds). That combo can cause a sudden, life-threatening drop in blood pressure. Also be careful with alpha-blockers for prostate or blood pressure, and some antifungals or antibiotics that affect CYP3A4 — they can raise sildenafil levels.

Alcohol and large fatty meals can blunt sildenafil’s effect and increase dizziness. If you take heart or blood pressure drugs, talk to your doctor before trying sildenafil.

Wondering how sildenafil compares to tadalafil (Cialis)? Tadalafil lasts much longer (up to 36 hours) and can be taken daily at low doses. Choose based on how often you plan sexual activity and how you tolerate side effects.

Buying online? Watch out for fakes. Articles on our site cover safe pharmacies and how to spot scams. Good signs: a legitimate pharmacy asks for a prescription, lists a licensed pharmacist, has clear contact details, and uses secure payment. Avoid sites offering huge discounts with no prescription — those pills are often counterfeit and risky.

If you’re new to ED meds, schedule a brief visit with your doctor or a licensed telehealth provider. They’ll check for causes (heart disease, diabetes, low testosterone), confirm it’s safe, and recommend the right dose or an alternative treatment.

Want deeper guides on buying Viagra, differences between ED drugs, or online pharmacy safety? Check related articles on our site for practical tips and real steps to protect your health and your wallet.