Sildenafil: What It Does, How to Use It, and Safety Tips

Sildenafil is best known as the active ingredient in Viagra. It helps many men with erectile dysfunction (ED) get and keep an erection by improving blood flow. It’s also used at different doses for pulmonary arterial hypertension (PAH). If you’re thinking about sildenafil, here’s the plain, useful info you need.

How it works: sildenafil blocks an enzyme called PDE5. That relaxes blood vessels in the penis and lungs, making it easier for blood to flow when you’re sexually aroused or to lower pressure in the lungs for PAH patients. It doesn’t cause arousal on its own — sexual stimulation is still required.

Practical dosing and timing

For ED, common doses are 25 mg, 50 mg, or 100 mg. Most people start at 50 mg. Take it 30–60 minutes before sex. It can work as early as 15 minutes for some, but plan for about an hour. Don’t take more than one dose in 24 hours. If 50 mg works fine but causes side effects, try 25 mg. If it’s not enough, talk to your doctor about 100 mg.

For pulmonary arterial hypertension (Revatio), the usual dose is 20 mg three times a day. That dosing is different from ED dosing, so follow what your prescriber tells you.

Side effects, interactions, and warnings

Common side effects are headache, flushing, indigestion, stuffy nose, and mild vision changes (like seeing a blue tint). Most effects are short-lived. Stop the drug and seek help if you get sudden vision loss, sudden hearing loss, chest pain, or an erection lasting more than 4 hours (this is a medical emergency).

Do not take sildenafil with nitrates (nitroglycerin or similar). Mixing them can cause a dangerous drop in blood pressure. Be careful if you take alpha-blockers or medicines that affect CYP3A4, like certain antifungals, HIV drugs, or some antibiotics — these can raise sildenafil levels and increase side effects. Grapefruit and grapefruit juice can also boost levels.

If you have heart disease, low blood pressure, severe liver problems, or certain eye conditions, check with your doctor before using sildenafil. Pregnant women should not use sildenafil except under specialist care for PAH.

Buying tips: always get a prescription. Use licensed pharmacies with clear contact info and real reviews. Beware of websites selling huge bulk amounts for very low prices — those pills can be fake. If buying online, confirm the pharmacy requires a prescription, shows a physical address, and has a pharmacist available to contact.

Final practical notes: try the drug in a relaxed setting when you can focus on intimacy. Keep a log of dose and effects to discuss with your doctor. If sildenafil doesn’t work after a few tries at an adjusted dose, your doctor can suggest alternatives or check for underlying medical issues.

If you want, I can summarize alternatives, safety checks for online pharmacies, or common drug interactions in a short list. Which would help you most?