Sildenafil at a glance
Medicine class
PDE5 inhibitor.
Main licensed uses
Erectile dysfunction and selected forms of pulmonary arterial hypertension.
Erectile dysfunction
Sexual stimulation is still needed; sildenafil does not produce an erection by itself.
What is Sildenafil used for?
Selected UK products cover two distinct licensed settings:
Erectile dysfunction in adult men who cannot achieve or maintain an erection sufficient for satisfactory sexual activity.
PAH in specified adults and children, including primary PAH and PAH associated with connective-tissue or congenital heart disease.
The injectable product is licensed for clinically stable adults with PAH who already receive oral Revatio but temporarily cannot take it by mouth.
Sildenafil is not authorised for fetal growth restriction; UK safety advice reports potential fetal and neonatal harm in this setting.
How does Sildenafil work?
Sildenafil blocks PDE5, reducing the breakdown of cyclic GMP. This promotes smooth-muscle relaxation, increasing penile blood flow during sexual stimulation and widening pulmonary blood vessels in PAH.
Sildenafil preparations and strengths
Oral suspension
Route: Oral
Strengths: 10 mg/mL
Tablet
Route: Oral
Strengths: 20 mg, 25 mg, 50 mg, 100 mg
How to take Sildenafil
Follow the product leaflet and instructions from the prescriber or pharmacist because administration differs by indication and formulation.
Swallow film-coated tablets with water. A meal may delay their effect when used for erectile dysfunction.
Shake reconstituted oral suspension vigorously before measuring it and use only the supplied oral syringe.
The oral suspension is normally prepared by a pharmacist and may be taken with or without food.
The intravenous formulation is given by healthcare professionals and is not for self-administration.
Avoid grapefruit juice during Revatio treatment because it may increase sildenafil exposure.
Sildenafil side effects
Common or expected effects
- Headache
- Flushing
- Indigestion or heartburn
- Nausea
- Dizziness
- Blocked nose
- Temporary blurred or colour-tinged vision
- Diarrhoea or limb pain, particularly during PAH treatment
Get urgent medical advice
- Chest pain, collapse or severe breathlessness
- A prolonged or painful erection
- Sudden reduction or loss of vision
- Sudden hearing loss
- Seizure
- Severe allergic reaction
Sildenafil in pregnancy
Sildenafil for erectile dysfunction is not indicated for women. PAH makes pregnancy exceptionally high risk. Anyone who becomes pregnant while taking sildenafil for PAH should not stop it without specialist advice and needs prompt review by a specialist heart-and-pregnancy team. PAH products advise use only when strictly necessary. Sildenafil must not be used to treat fetal growth restriction.
Sildenafil while breastfeeding
Sildenafil interactions
Check all prescribed, pharmacy, recreational and herbal products before using sildenafil.
Nitrates and nitric-oxide donors, including glyceryl trinitrate, isosorbide medicines and amyl nitrite ('poppers')
The combination can cause a dangerous fall in blood pressure and is contraindicated.
Riociguat
Concurrent use is contraindicated because additive blood-pressure lowering can cause symptomatic hypotension.
Common questions about Sildenafil
Answers are fully visible for fast scanning and source review.
Does sildenafil cause an erection without sexual stimulation?
No. For erectile dysfunction, it supports the normal response to sexual stimulation but does not create sexual desire or an automatic erection.
Can sildenafil be taken with glyceryl trinitrate spray?
No. Glyceryl trinitrate and other nitrates can combine with sildenafil to cause a dangerous fall in blood pressure.
What should I do if I develop chest pain after taking sildenafil?
Call 999. Do not treat the pain with nitrates, and tell emergency staff that sildenafil was taken.
Can alcohol be used with sildenafil?
Alcohol is not directly prohibited, but larger amounts can worsen dizziness, lower blood pressure and make erections more difficult.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.