Sildenafil is a prescription medication that belongs to a class called PDE-5 inhibitors. It’s used for two main conditions:
- Erectile dysfunction (ED) in men
- Pulmonary arterial hypertension (PAH)
Brand names: Viagra (for ED) and Revatio (for PAH). Generic sildenafil is also available.
What it does (mechanism)
- In ED: Enhances blood flow to the penis in response to sexual stimulation by increasing levels of a messenger (cGMP) that relaxes blood vessels.
- In PAH: Dilates the small arteries in the lungs, helping to lower the workload on the heart.
How to take and typical dosing
- For ED:
- Common starting dose: 50 mg as needed, about 30–60 minutes before sexual activity.
- Dose can be adjusted to 25 mg or 100 mg depending on effectiveness and side effects.
- Typical maximum is 100 mg per day, and it should not be taken more than once per day.
- It can be taken with or without a meal; high-fat meals may delay onset.
- For PAH:
- Typical adult dose (Revatio): 20 mg taken three times daily.
- Dosing may be adjusted for kidney or liver impairment; your doctor will tailor this.
- Usually continued as part of a daily treatment plan, not just “as needed.”
Onset and duration
- ED: Effects usually start within 30–60 minutes; can last for several hours. Sexual activity should be possible during this window.
- PAH: Dosing is spread through the day (three times daily); effort and exercise tolerance may improve over weeks.
Common side effects
- Headache, flushing, indigestion (dyspepsia)
- Nasal congestion, dizziness
- Visual changes (e.g., a blue-tinged tint to vision) in a small number of people
- Back pain or muscle aches (more common with higher doses)
Serious but less common risks
- Sudden vision or hearing loss
- Priapism (an erection lasting more than 4 hours) – seek urgent medical care
- Severe low blood pressure, especially with nitrates
Important drug interactions and contraindications
- Nitrates (e.g., nitroglycerin, isosorbide dinitrate): Do not use sildenafil if you are taking nitrates. This can cause a dangerous drop in blood pressure.
- Riociguat: Do not use sildenafil with riociguat.
- Alpha-blockers (some blood pressure meds for enlarged prostate or high blood pressure): can cause low blood pressure; start at a low dose and monitor with a clinician.
- Other PDE-5 inhibitors or certain strong inhibitors of CYP3A4/CYP2C9 (enzyme systems that metabolize sildenafil): may require dose adjustments.
- Allergies to sildenafil or any inactive ingredients.
Special populations and warnings
- Do not use if you have severe cardiovascular disease where sexual activity is not recommended unless advised by a doctor.
- Caution if you have eye or vision problems, bleeding disorders, or very low blood pressure.
- Liver or kidney impairment may require dose adjustments.
- Vision changes, hearing changes, or priapism require medical attention.
What to tell your doctor before taking
- Other medications you’re taking (especially nitrates, nitric oxide donors, certain blood pressure meds, antifungals like ketoconazole, ritonavir, or clarithromycin).
- Any history of heart disease, strokes, low blood pressure, or eye problems.
- If you have a high-risk for sexual activity due to your health.
Pregnancy and breastfeeding
- Sildenafil is not intended for use in pregnancy or breastfeeding. It’s not approved for use in women for ED.
Storage
- Room temperature, away from moisture and heat. Keep out of reach of children.
If you’d like, tell me:
- Are you asking about ED or PAH use?
- Do you want dosing specifics, safety considerations, or potential drug interactions for your situation?
- Any other meds you’re taking or health conditions I should consider?
Note: This is general information and not a substitute for medical advice. If you’re considering sildenafil, talk with a healthcare provider to confirm it’s appropriate for you and to get dosing tailored to your health. If you experience an erection lasting more than 4 hours, chest pain, fainting, or sudden vision/hearing loss, seek urgent medical care.