At a Glance
Oral sildenafil is FDA‑approved to treat erectile dysfunction in adult men and, under brand Revatio, pulmonary arterial hypertension in adults and some children (1 year and older).
Generic/Biosimilar name: Sildenafil.
Active ingredient: Sildenafil Citrate.
Administration route: Oral.
Typical oral sildenafil doses are 25–100 mg once as needed about 1 hour before sexual activity for erectile dysfunction, or 5–20 mg three times daily for pulmonary arterial hypertension.
How It Works
- Sildenafil blocks an enzyme called PDE5, which normally breaks down a natural chemical (cGMP) that relaxes blood vessels.
- By preserving cGMP, it helps blood vessels relax and widen, improving blood flow where PDE5 is active (such as the penis and lungs).
- For erectile dysfunction, sexual stimulation is still needed for an erection; sildenafil just makes the blood-flow response stronger.
Treatment and Efficacy
Approved indications
Oral sildenafil is approved to treat erectile dysfunction in adult men and pulmonary arterial hypertension (WHO Group 1) in adults and children 1 year and older to improve exercise ability and delay clinical worsening.
Off‑label uses and evidence
Clinicians sometimes use sildenafil off‑label for certain high‑altitude illnesses, Raynaud phenomenon, or other forms of pulmonary hypertension; evidence ranges from small clinical trials to observational studies and is more limited than for approved uses.
Efficacy expectations
For erectile dysfunction, many patients notice improved erections within 30–60 minutes of a dose, with effect lasting about 4 hours and response rates generally higher than placebo and comparable to other PDE5 inhibitors such as tadalafil and vardenafil. For pulmonary arterial hypertension, benefits such as improved exercise capacity and symptoms usually appear over weeks, with clinical trials showing better 6‑minute‑walk distance and delayed worsening versus placebo; overall effectiveness is similar to other oral PAH vasodilators when used appropriately and often as part of combination therapy.
Dosage and Administration
Typical dosing and how to take
For erectile dysfunction, adults usually take 50 mg by mouth about 1 hour before sexual activity, with possible adjustment to 25–100 mg based on response and tolerability, no more than once daily; it can be taken 30 minutes to 4 hours before sexual activity and may work a bit slower with a high‑fat meal. For pulmonary arterial hypertension, typical adult dosing is 20 mg by mouth three times daily (about 4–6 hours apart), with pediatric dosing based on weight; tablets are swallowed with water and may be taken with or without food.
Special dosing instructions
Lower starting doses (often 25 mg for erectile dysfunction) are recommended in older adults, in significant kidney or liver disease, or when used with certain interacting drugs (such as strong CYP3A4 inhibitors). Patients should not take multiple erectile dysfunction doses in a day or combine sildenafil with other PDE5 inhibitors.
Missed dose and overdose guidance
For erectile dysfunction, if a planned dose is missed, take it when needed, observing at least 24 hours between doses. For pulmonary arterial hypertension, if a dose is missed, take it as soon as remembered unless it is almost time for the next dose, in which case skip the missed dose and resume the regular schedule without doubling. In suspected overdose (for example, taking much more than prescribed or severe symptoms such as fainting, chest pain, or persistent priapism), seek emergency medical attention or contact poison control right away.
Safety and Side Effects
Common side effects
Frequent effects include headache, facial flushing, indigestion, nasal congestion, dizziness, and mild visual changes (such as a blue tint or increased light sensitivity); these usually begin within a few hours of a dose and are typically mild to moderate and short‑lived.
Serious or rare adverse effects
Seek immediate care for chest pain, signs of a heart attack or stroke, sudden loss of vision in one or both eyes, sudden decrease or loss of hearing (sometimes with ringing or dizziness), a painful erection lasting more than 4 hours (priapism), severe shortness of breath, or signs of an allergic reaction such as swelling of the face, lips, tongue, or throat.
Warnings and precautions
Use is contraindicated with nitrates or riociguat because of the risk of dangerous blood pressure drops, and it should be used cautiously in people with significant heart disease, low blood pressure, recent heart attack or stroke, severe liver impairment, or advanced kidney disease. It is generally not recommended in pregnancy for erectile dysfunction and is used in pregnancy for pulmonary arterial hypertension only when potential benefits outweigh risks; limited information suggests small amounts pass into breast milk, so breastfeeding decisions should be individualized with a clinician. Dose adjustments or extra monitoring may be needed in older adults, those with hepatic or renal impairment, and those taking interacting medicines.
Relative safety profile and safety updates
Overall, sildenafil has a well‑established safety profile when prescribed appropriately, similar to other PDE5 inhibitors, but the cardiovascular and visual warnings make correct patient selection important. Patients in the United States can report side effects to the FDA MedWatch program and can check the FDA website for the latest safety communications on sildenafil‑containing products.
Interactions and Precautions
Key drug and substance interactions
Sildenafil must not be used with nitrates (such as nitroglycerin, isosorbide dinitrate, or isosorbide mononitrate) or with riociguat due to the risk of profound drops in blood pressure. Strong CYP3A4 inhibitors (like ketoconazole, itraconazole, ritonavir, or clarithromycin) can greatly increase sildenafil levels, requiring lower doses, while certain CYP3A4 inducers (such as rifampin or some anticonvulsants) may reduce its effectiveness. Other blood pressure–lowering agents, alpha‑blockers, and heavy alcohol use can add to blood‑pressure‑lowering effects and dizziness. There are no major food restrictions, but a high‑fat meal may delay onset; common supplements without cardiovascular effects are less likely to interact, but products marketed for sexual enhancement or containing nitrates or vasodilators may pose added risk.
Precautions and conditions making use unsafe or higher risk
Sildenafil is generally avoided or used only under specialist guidance in people with unstable angina, severe heart failure, very low blood pressure, uncontrolled hypertension, recent myocardial infarction or stroke, serious arrhythmias, severe liver impairment, advanced kidney failure requiring dialysis, or certain inherited eye disorders (such as retinitis pigmentosa). Caution is also needed in patients with anatomical penile deformities or conditions that predispose to priapism (like sickle cell disease, leukemia, or multiple myeloma).
Monitoring needs
For erectile dysfunction, routine lab monitoring is usually minimal, but blood pressure and overall cardiovascular status should be periodically reviewed. For pulmonary arterial hypertension, ongoing monitoring often includes blood pressure, heart rate, symptoms, exercise capacity, and sometimes echocardiograms and relevant blood tests as part of comprehensive PAH care.
Common Questions and Answers
Q: How long does sildenafil take to work and how long does it last?
A: Most people feel the effect within 30–60 minutes after an oral dose, and the ability to get an erection is typically improved for about 4 hours, although this varies by person.
Q: Can I take sildenafil every day?
A: Many people safely use sildenafil as needed up to once daily for erectile dysfunction, but the exact regimen should follow a clinician’s instructions, especially if you have heart disease or take other medications.
Q: Is it safe to drink alcohol while taking sildenafil?
A: Small amounts of alcohol are usually tolerated, but larger amounts can lower blood pressure, increase dizziness, and worsen erectile function, so heavy drinking around the time of a dose is discouraged.
Q: Can women or children use sildenafil?
A: Sildenafil is not approved for treating sexual dysfunction in women and should not be used for this purpose, but it is approved under specialist supervision for pulmonary arterial hypertension in adults and children 1 year and older.
Q: What if sildenafil doesn’t work for me?
A: If you do not get adequate results after trying several doses as directed, talk with your clinician, who can check for contributing conditions, review interacting medicines, adjust the dose, timing, or food intake, or consider alternative therapies.
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Disposal Guidance
Storage
Store sildenafil tablets at room temperature (about 68–77°F / 20–25°C), away from excess heat, moisture, and light, and keep them in the original, tightly closed container out of reach of children and pets.
Disposal
Do not flush unused tablets unless specifically instructed; use community drug take‑back programs when available or follow local guidance for mixing tablets with an unappealing substance (like used coffee grounds) in a sealed container before placing in household trash.