Sildenafil — what it does and what you should know

Sildenafil is the active drug most people associate with treating erectile dysfunction (ED). It can also treat pulmonary arterial hypertension (PAH) at different doses. If you’re thinking about using sildenafil, this guide tells you how it works, what to watch for, and how to buy it safely online without falling for shady sellers.

How sildenafil works and when it helps

Sildenafil relaxes blood vessels and increases blood flow to certain areas. For ED, it helps achieve and maintain an erection when sexually stimulated. Many men notice effects in 30–60 minutes, and the effect can last a few hours. For PAH, sildenafil lowers blood pressure in the lungs and improves exercise capacity — the dose and schedule are different from ED treatment.

Don’t expect it to work without sexual arousal. If you have sudden vision loss, chest pain, or an erection lasting more than 4 hours (priapism), get emergency care.

Dosage, common side effects, and interactions

For ED, doctors commonly start patients on 25–50 mg taken about an hour before sex and adjust to 25–100 mg based on effect and tolerance. For PAH, the prescription form and dose usually differ (often multiple times per day) — follow your prescriber’s instructions exactly. Older adults and people with liver or kidney problems may need lower doses.

Common side effects are headache, flushing, nasal congestion, indigestion, and dizziness. Less common but serious risks include a sudden drop in blood pressure, vision changes, hearing loss, and priapism. Avoid sildenafil if you take nitrates (nitroglycerin, isosorbide) — the combination can cause dangerous low blood pressure. Also be careful with alpha-blockers, some blood pressure meds, and strong CYP3A4 inhibitors like certain antifungals or HIV protease inhibitors; these can raise sildenafil levels and increase side effects. Grapefruit juice can also increase drug levels.

Tell your doctor about heart disease, recent stroke, uncontrolled high blood pressure, severe liver or kidney disease, or retinal disorders before using sildenafil.

Thinking about buying sildenafil online? Check reviews, confirm the pharmacy requires a valid prescription, and look for pharmacy credentials and secure payment. Avoid stores that offer large discounts with no prescription or push multiple pills without medical questions. A legitimate online pharmacy will list contact info, verify a prescription, and use secure checkout. If it sounds too good to be true, it probably is.

Sildenafil is a useful, well-studied medicine when used properly. Use it under medical advice, follow dosing guidelines, watch for interactions, and choose reputable pharmacies—online or local. If you’re unsure whether sildenafil is right for you, a quick chat with a doctor or pharmacist will clear things up fast.