Viagra or Sildenafil is a medicine used to treat erectile dysfunction. It increases blood flow to the penis to help men get an erection. At least two-thirds of men have improved erections after taking it.

Viagra is also sometimes used to treat pulmonary hypertension (high blood pressure in the blood vessels that supply the lungs).

This medicine is available on prescription and can also be bought from most pharmacies. It comes as tablets that you swallow, chewable tablets, and as a liquid that you drink.

• It usually takes 30 to 60 minutes for sildenafil to work for erectile dysfunction. You can take it up to 4 hours before you want to have sex.
• Taking Viagra alone will not cause an erection. You need to be aroused for it to work.
• The most common side effects are headaches, feeling sick, hot flushes and dizziness. Many men have no side effects or only mild ones.
• It can be dangerous to take sildenafil if you also take medicines called nitrates (often given for chest pain). The combination can cause a dangerous fall in your blood pressure. If you’re not sure if you’re taking a nitrate, ask your doctor or pharmacist.
• Sildenafil is called by the brand names Viagra (for erectile dysfunction) and Revatio (for pulmonary hypertension).

Sildenafil for erectile dysfunction (Viagra) can be taken by men aged 18 and over. It’s not for women or children.

Viagra for pulmonary hypertension (Revatio) can be taken by adults and children aged 1 and over.

Viagra is not suitable for some people.

Do not take sildenafil if you:

• have had an allergic reaction to sildenafil (Viagra) or any other medicines in the past
• are taking medicines called nitrates for chest pain
• have a serious heart or liver problem
• have recently had a stroke or a heart attack
• have low blood pressure
• have a rare inherited eye disease, such as retinitis pigmentosa

Check with your doctor before taking sildenafil if you:

• have sickle cell anaemia (an abnormality of red blood cells), leukaemia (cancer of blood cells) or multiple myeloma (cancer of bone marrow)
• have a deformity of your penis or Peyronie’s disease (curved penis)
• have a heart problem. Your doctor should carefully check whether your heart can take the additional strain of having sex.
• have a stomach ulcer or a bleeding problem like haemophilia

It’s important to take it as advised by your doctor or pharmacist.

How much will I take for erectile dysfunction?

Viagra tablets for erectile dysfunction come in different strengths ranging from 25mg to 100mg.

The usual dose is 50mg, when you need it (no more than once a day).

The dose can be increased to 100mg or decreased to 25mg depending on its effect.

Take sildenafil up to 4 hours before you want to have sex. For sildenafil to work properly, you’ll need to be sexually excited.

How much will I take for pulmonary hypertension?

Viagra tablets for pulmonary hypertension come in 10mg and 20mg tablets.

The usual adult dose is 20mg taken 3 times a day.

Doses for children can range from 10mg to 20mg taken 3 times a day, depending on their weight.

How to take it

Swallow tablets whole with a glass of water or juice (but not grapefruit juice).

For erectile dysfunction, it’s best to take sildenafil on an empty stomach. It may take longer to work if you take it with food.

What if I forget to take it?

If you have pulmonary hypertension and you forget to take a dose of Viagra, take it as soon as you remember and then continue as usual.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you often forget doses, it may help to set an alarm to remind you.

You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

Taking too much Viagra by accident can cause unpleasant side effects, such as:

• headaches
• dizziness
• indigestion
• blocked nose
• altered vision

 

Like all medicines, sildenafil can cause side effects in some people. Many people have no side effects or only minor ones.

Common side effects

Common side effects happen in more than 1 in 100 people.

If you get these side effects, keep taking the medicine, but tell your doctor or pharmacist if these side effects bother you or do not go away:

• headaches
• feeling sick
• hot flushes, including facial flushing
• indigestion
• a color tinge to your vision or blurred vision
• stuffy nose
• dizziness

Serious side effects

however, Serious side effects are rare and happen in less than 1 in 1,000 people.

Stop taking sildenafil and call a doctor straight away if you get:

• chest pains – if this happens during or after sex, get into a semi-sitting position and try to relax; do not use nitrates to treat your chest pain
• prolonged and sometimes painful erections – if you have an erection that lasts for more than 4 hours, contact a doctor immediately
• a sudden decrease or loss of vision
• a serious skin reaction – symptoms may include fever, severe peeling and swelling of the skin, blistering of the mouth, genitals and around the eyes
• seizures

Serious allergic reaction

In rare cases, it’s possible to have a serious allergic reaction (anaphylaxis) to sildenafil.