Sildenafil

Generic name

Sildenafil

Active ingredient

Sildenafil (variants: sildenafil citrate)

Product type

Small-molecule medicine

Drug class

PDE5 inhibitors

Brand names

UK Viagra, Viagra Connect, Aronix, Liberize, Nipatra, Revatio, Grandipam

Routes

Oral

Dosage forms

Tablet, Solution

Also known as

Viagra, Revatio, Viagra Connect

Usual preparations

Tablets and a liquid. (summary of the cited reference, not a prescription)

Onset and duration

The NHS says it usually takes 30 to 60 minutes to work for erection problems.

Monitoring

The NHS asks people to tell a pharmacist or doctor about other medicines, including herbal remedies, vitamins and supplements, before starting. Local NHS prescribing guidance suggests a follow-up review after starting to check whether the treatment is working.

Availability by country

Legal status differs between countries and can change; each row cites the document it was taken from and applies only to the country named.

What it is used for

• Erection problems (erectile dysfunction), the use the NHS names first.
• Pulmonary hypertension, which is high blood pressure in the blood vessels that supply the lungs.
• Second-line treatment for Raynaud's phenomenon and digital ulcers, according to one NHS hospital leaflet.

How it works in the body

Sildenafil belongs to a group of medicines called PDE5 inhibitors. For erection problems, the NHS says it temporarily increases blood flow to the penis when a person is sexually aroused. In pulmonary hypertension, it relaxes blood vessels in the chest. Taken alone it does not cause an erection, and sexual excitement is needed for it to work.

Cautions and interactions

• Nitrates, often given for chest pain, can cause a dangerous fall in blood pressure with sildenafil.
• The NHS says taking sildenafil with poppers (amyl nitrate) or illegal drugs such as amphetamines, ecstasy and cocaine can increase the risk of serious side effects.
• The NHS asks people to tell a pharmacist or doctor about riociguat, heart medicines, epilepsy medicines, HIV medicines, antifungals and St John's wort.
• An NHS Highland guideline says sildenafil is contraindicated with nicorandil.
• A review says alpha-blockers call for caution when used with PDE5 inhibitors.
• UK product information says grapefruit juice is not recommended with sildenafil.
• Heavy drinking can make erections harder to get.
• The NHS lists a past allergic reaction, nitrates for angina, low blood pressure and a recent stroke or heart attack among the reasons sildenafil may not be suitable.
• It also lists a rare inherited eye disease such as retinitis pigmentosa and a curved penis (Peyronie's disease).
• A formulary note lists past sudden vision loss from reduced blood flow to the optic nerve as a reason to avoid it.
• For erection problems the NHS says sildenafil is not usually used in pregnancy.
• The NHS says it does not usually cause sleepiness, but driving or cycling is not advised if it causes dizziness or blurred vision.

Interactions

Interactions documented in the official sources cited on each card. The list covers the medicines represented on this site and is not exhaustive; how the interaction data is compiled.

No pair records for this medicine are in the sources currently represented by Anatomy Nexus. Absence from this list does not mean no interaction exists.

Same-class and related medicines

Same class: PDE5 inhibitors

Medicines that share the class of Sildenafil. They are separate medicines with their own licences, doses and interactions, not alternative names for Sildenafil.

Related medicines

Medicines often discussed alongside Sildenafil: used together, compared with it, or acting on the same problem by a different route.

Key facts

What is sildenafil used for?

Sildenafil is a medicine used to treat erection problems, also called erectile dysfunction. The NHS says it is also sometimes used for pulmonary hypertension, which is high blood pressure in the blood vessels that supply the lungs. Most men aged 18 and over can use it for erection problems. Most adults and children aged 1 year and over can use it for pulmonary hypertension. Brand names for the erection use include Viagra, Aronix, Liberize and Nipatra.

The NHS says women can take sildenafil for pulmonary hypertension, but there is no good evidence that it helps sexual problems in women. A hospital leaflet describes sildenafil as a second-line treatment for Raynaud's phenomenon and for digital ulcers. Local NHS prescribing guidance says generic sildenafil can be prescribed on the NHS where clinically appropriate, while branded Viagra is limited to men who meet set criteria. Private prescriptions are an option for people who do not qualify. The MHRA has reclassified Viagra Connect tablets as a pharmacy medicine.

How does sildenafil work?

Sildenafil belongs to a group of medicines called PDE5 inhibitors. StatPearls says these medicines stop the PDE5 enzyme from breaking down a chemical messenger called cGMP. For erection problems, the NHS says sildenafil temporarily increases blood flow to the penis when a person is sexually aroused. Taken alone it does not cause an erection. In pulmonary hypertension, it relaxes blood vessels in the chest. The NHS says it does not affect any type of contraception, including the combined pill and emergency contraception.

If it does not seem to work, the NHS lists the timing of the dose or a lack of sexual arousal as possible reasons. Other options the NHS lists for erection problems include a vacuum pump, psychological treatments, penile implants and pelvic floor exercises. The NHS also lists losing weight, stopping smoking, a healthy diet, regular exercise and reducing stress and anxiety as steps that can help.

What are the side effects of sildenafil?

Common side effects include headache, indigestion, dizziness and a blocked nose. Many people have no side effects or only mild ones. The NHS says serious side effects are rare. The NHS says the medicine can be taken for a long time, with no lasting harmful effects seen over many months or years.

A painful erection that lasts a long time is listed as a serious side effect, and the advice is to call 999 or go to A&E. For suspected anaphylaxis, a heart attack or a seizure, the NHS gives 999. For a sudden decrease or loss of vision, the NHS says to stop taking sildenafil and call a doctor or NHS 111 straight away. MedlinePlus says the vision loss was permanent in some cases. MedlinePlus also advises calling a doctor right away for a sudden decrease or loss of hearing.

Taking sildenafil with other medicines, drugs and alcohol

The NHS says it can be dangerous to take sildenafil with nitrates, which are often given for chest pain. The combination can cause a dangerous fall in blood pressure. Taking sildenafil with poppers (amyl nitrate) or illegal drugs such as amphetamines, ecstasy and cocaine can increase the risk of serious side effects.

The NHS asks people to tell a pharmacist or doctor about riociguat, heart medicines, epilepsy medicines, HIV medicines, antifungals and St John's wort. It also says it cannot confirm that herbal remedies and supplements are safe with sildenafil, because they are not tested in the same way as pharmacy and prescription medicines. UK product information says grapefruit juice is not recommended. The NHS says heavy drinking can make erections harder to get.

Who needs extra care with sildenafil?

The NHS lists a past allergic reaction to sildenafil, nitrates taken for angina, low blood pressure and a recent stroke or heart attack among the reasons it may not be suitable. It also lists a rare inherited eye disease such as retinitis pigmentosa and a curved penis (Peyronie's disease).

A formulary note lists past sudden vision loss from reduced blood flow to the optic nerve as a reason to avoid it. For erection problems, the NHS says sildenafil is not usually used in pregnancy. The NHS says it does not usually cause sleepiness, but driving or cycling is not advised if it causes dizziness or blurred vision.

Frequently asked questions