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How and when to take sildenafil

It's important to take sildenafil as advised by a doctor or pharmacist.

Dosage and strength for erectile dysfunction

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

The usual dose is 50mg, when you need it. Do not take it 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.

Dosage and strength for pulmonary hypertension

Sildenafil tablets for pulmonary hypertension come in 10mg and 20mg strengths.

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. Do not take it more than 3 times a day.

How to take tablets

Swallow tablets whole with a drink 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.

How to take liquid

If you or your child are taking sildenafil as a liquid, 1ml is usually the same as taking a 10mg tablet, but it's important to always check the medicine label.

Liquid sildenafil will usually be made up for you by your pharmacist.

The medicine will come with a plastic syringe or spoon to help you take the right amount. If you do not have a plastic syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not measure the right amount.

If you forget to take it

If you have pulmonary hypertension and you forget to take a dose of sildenafil, take it as soon as you remember unless it's nearly time for your next dose. In this case, just leave out the missed dose and take your next dose at the usual time.

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.

If you take too much

Taking too much sildenafil can cause unpleasant side effects.

Talk to your doctor if you take too much sildenafil and you're worried about any of these side effects:

  • headaches
  • dizziness
  • indigestion
  • blocked nose
  • changes to your vision

Page last reviewed: 2 March 2022
Next review due: 2 March 2025