Sildenafil: What it does, how to use it, and what to watch for

Sildenafil is the active drug in well-known ED medicines (like Cenforce) and is also used for pulmonary arterial hypertension (PAH). It helps increase blood flow by relaxing blood vessels, which usually means better erections for roughly 7 in 10 men with erectile dysfunction and improved exercise tolerance for people with PAH.

How to take sildenafil

For erectile dysfunction the common dose is 25–100 mg, taken about 30–60 minutes before sex. Start low if you’re over 65, have liver or kidney issues, or take interacting meds. Do not take more than one dose in 24 hours. For pulmonary hypertension, dosing and schedules are different (for example, prescription Revatio is often 20 mg three times daily), so follow the exact directions from your doctor.

High-fat meals can slow absorption, so taking sildenafil after a heavy meal may delay its effect. Alcohol makes side effects like dizziness worse, and heavy drinking can reduce effectiveness.

Important safety warnings and interactions

Never mix sildenafil with nitrates (nitroglycerin, isosorbide mononitrate/ dinitrate). The combo can cause a dangerous drop in blood pressure. Also be careful with strong CYP3A4 inhibitors—drugs like ritonavir, some azole antifungals, or certain HIV medications can raise sildenafil levels and increase side effects.

Common side effects include headache, flushing, indigestion, nasal congestion, and temporary visual changes (a blue tint or sensitivity to light). If you get sudden vision loss, chest pain, fainting, or an erection lasting more than 4 hours (priapism), get emergency help right away.

Tell your doctor about heart disease, low blood pressure, recent stroke, severe liver or kidney problems, or if you take alpha-blockers for prostate symptoms—doses may need adjusting.

If you’re on multiple heart medicines or HIV treatments, ask your prescriber how to safely use sildenafil and what dose to try first.

Buying sildenafil online: be cautious. Only use pharmacies that ask for a prescription, show verifiable credentials (look for CIPA/NABP seals) and have clear contact details. Avoid sites that offer huge discounts without prescription checks—these often sell fakes or unsafe products. Check the active ingredient and manufacturer on the label; generic sildenafil from reputable manufacturers is usually fine and cheaper than brand-name products.

Want to double-check a site? Look for real customer reviews, clear refund and privacy policies, and a reachable pharmacist or medical contact. If something feels off—extreme low prices, no prescription required, or badly written product pages—walk away.

Sildenafil can be safe and effective when used correctly. Talk with your doctor about your heart health and other medicines first, get a proper prescription, and choose a trustworthy pharmacy when buying online. That way you get the benefit without the unnecessary risk.