Sildenafil (Viagra)

What sildenafil is for

Sildenafil is mainly used to treat erection problems (erectile dysfunction).

It's also used to treat pulmonary arterial hypertension.

How to take sildenafil

Sildenafil usually comes as tablets or a liquid that you swallow.

How much you need to take and how long for depends on why you're taking it. If a doctor has prescribed it, they will tell you how much to take and how often.

Always check the packet or leaflet that comes with your medicine. Ask a pharmacist or doctor for advice if you're not sure how to take it or have any problems taking it.

People with erection problems are usually told to take 1 tablet 1 hour before sex, but the amount of time it takes to work can vary. Do not take more than 1 tablet a day as the effects can last up to 36 hours.

Swallow the tablet whole with some water.

If you miss a dose of sildenafil

If you're taking sildenafil for pulmonary arterial hypertension, and you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose.

If it's nearly time for your next dose, skip the dose you missed and take your next dose at the usual time.

Do not take 2 doses to make up for a missed dose.

If you take too much sildenafil

Taking too much sildenafil can be dangerous.

If you're told to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.

Bring the sildenafil packet or leaflet inside it, any remaining medicine, and any other medicines you take.

Side effects of sildenafil

Like all medicines, sildenafil can cause side effects, but not everyone gets them.

Common side effects

Common side effects of sildenafil can include:

• headache
• dizziness
• blocked or stuffy nose
• stomach ache, diarrhoea or feeling sick (nausea)
• anxiety
• temporary changes in vision, such as blurred vision

If you feel dizzy or have blurred vision after taking sildenafil, do not drive, ride a bike or use machinery until you no longer have these symptoms.

Serious side effects

Sildenafil can sometimes cause serious side effects, although most of them are rare.

Possible serious side effects of sildenafil can include:

• an allergic reaction (anaphylaxis) – causing symptoms such as a swollen throat or tongue, a raised itchy rash and difficulty breathing
• blistering skin around the mouth, eyes, nose or genitals, with flu-like symptoms
• heart attack – causing symptoms such as chest pain that feels tight or like squeezing on your chest, feeling short of breath, and sweating
• a fast or irregular heartbeat
• seizures (fits)
• fainting
• painful erections that last longer than 4 hours (priapism)

Who can and cannot take sildenafil

Most adults can take sildenafil.

But sildenafil is not suitable for everyone. For example, it may not be suitable if:

• you've ever had an allergic reaction or serious side effect from sildenafil
• you've recently had a heart attack or stroke
• you have low blood pressure or uncontrolled high blood pressure
• you have liver or kidney problems
• you have blood cancer (leukaemia) or cancer of the bone marrow (multiple myeloma)
• you have sickle cell anaemia
• you've ever had vision loss caused by reduced blood flow to the optic nerve (non-arteritic anterior ischemic optic neuropathy)
• you have a curved or bent penis, which makes getting an erection painful or difficult

Before taking sildenafil, tell your doctor if you have any medical conditions.

Breastfeeding and sildenafil

Tell your doctor if you're breastfeeding. Sildenafil is not usually used while breastfeeding. You doctor may offer a different treatment.

Pregnancy and sildenafil

Tell your doctor if you're pregnant or trying to get pregnant. Sildenafil is not usually used during pregnancy, but your doctor my recommend it if the benefits outweigh the risks.

Find out more about taking sildenafil during pregnancy on the Bumps (Best Use of Medicines in Pregnancy) website

Taking sildenafil with other medicines, food and drink

There are some medicines and supplements that may not mix well with sildenafil.

This includes some types of:

• heart medicines, such as nitrates for chest pain (angina)
• epilepsy medicine (anticonvulsants)
• medicine for pulmonary hypertension or high blood pressure
• antibiotics, including rifampicin, erythromycin and clarithromycin
• medicine for enlarged prostate or erectile dysfunction
• medicine for HIV or AIDS
• antifungal medicines
• supplements containing St John's Wort

Taking sildenafil together with poppers (amyl nitrate) or illegal drugs, such as amphetamines, ecstasy and cocaine, can increase the risk of serious side effects.

This is not the full list of medicines that may not mix well with sildenafil. Before taking it, tell your doctor if you’re taking any other medicines, herbal remedies, vitamins or supplements.

Food, drink and alcohol with sildenafil

You can generally eat as normal while taking sildenafil, but do not eat grapefruit or drink grapefruit juice because it can make it more likely you'll get side effects.

You may find it takes longer to get an erection if you take it after eating a large meal.

It's best to avoid drinking too much alcohol when taking sildenafil because it can make getting an erection more difficult.