Sildenafil is a medicine most people know as Viagra. It helps many men with erectile dysfunction (ED) by increasing blood flow to the penis. Doctors also prescribe a different dose for pulmonary arterial hypertension under the brand Revatio. If you want quick, useful facts you can act on, read on.
How it works: sildenafil blocks an enzyme called PDE5. That makes the muscle in the blood vessels relax, letting more blood into the penis during sexual arousal. It doesn’t cause an erection on its own—you still need sexual stimulation.
For ED the common tablet strengths are 25 mg, 50 mg, and 100 mg. Most people start at 50 mg and adjust up or down with their doctor. Take sildenafil 30–60 minutes before sex. On an empty stomach it works faster; a heavy meal, especially fatty food, can slow it down. Effects usually last up to four hours, though this varies.
For pulmonary hypertension the dose and schedule differ (often 20 mg three times daily) — follow the exact prescription from your doctor.
Avoid sildenafil if you take any nitrate medicine (like nitroglycerin) for chest pain. Combining them can cause a dangerous drop in blood pressure. Also be cautious with alpha-blockers for prostate problems or high blood pressure—start at a low dose and monitor for dizziness.
Certain antifungals (ketoconazole), antibiotics (clarithromycin), and HIV protease inhibitors (ritonavir) can raise sildenafil levels. Tell your doctor about all meds and supplements you use. Don’t mix sildenafil with recreational drugs called "poppers" (amyl nitrite) — that’s risky.
Common side effects are headache, flushing, nasal congestion, indigestion, and mild changes in vision (a blue tint). Rare but serious risks include sudden vision loss, hearing loss, or a painful erection lasting more than four hours (priapism). If you have chest pain, sudden vision or hearing changes, or an erection over four hours, get medical help right away.
People with heart disease, uncontrolled high or low blood pressure, severe liver or kidney problems, or recent stroke should check with their doctor before using sildenafil. Older adults may need lower starting doses.
Thinking about buying online? Only use licensed pharmacies that require a prescription and list clear contact details. Avoid sellers offering suspiciously low prices or offering to skip a prescription. When in doubt, ask your doctor or pharmacist.
If ED is new or severe, it can signal diabetes, high blood pressure, or heart disease. A quick talk with your doctor can uncover causes and other treatments. Besides pills, options include lifestyle changes (losing weight, quitting smoking), devices, injections, or counseling when anxiety plays a role.
Store sildenafil at room temperature, away from moisture and heat. Keep it in the original packaging and out of reach of children.
Got questions about a specific dose or interaction? Ask your prescriber—getting the right advice is the safest move.
