Sildenafil (Viagra)

Sildenafil is used to treat erectile dysfunction and pulmonary arterial hypertension.

Sildenafil usually comes as a tablet that you take once a day. Follow the instructions that come with your medicine.

Side effects of sildenafil include headache, dizziness, a blocked nose and stomach ache. More serious side effects are rare.

Sildenafil is suitable for most adults and sometimes suitable for children, but always check before taking it because it's not suitable for everyone.

Taking sildenafil with other medicines, such as some heart and high blood pressure medicines, can cause problems. Always check before taking it.

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

It's also used to treat pulmonary arterial hypertension.

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.

Sildenafil is not usually prescribed together with nitrates. Ask a pharmacist or doctor for advice if you take nitrates such as glyceryl trinitrate (GTN) for chest pain.

If you buy sildenafil without a prescription, you're advised to have a check-up with your doctor within 6 months of starting it. Erection problems can be a sign of other serious health conditions, such as diabetes or heart problems.

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.

• you've taken more than your prescribed dose of sildenafil than it says on the packet, leaflet or prescription

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.

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.

• you have any side effects that bother you or do not go away

They may be able to give you advice about how you can reduce the side effects. Keep taking your medicine unless you're advised to stop.

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)

• you're taking sildenafil and think you might be having anaphylaxis, a heart attack or a seizure

If you think you're having any other serious side effects, call NHS 111.

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.

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.