Sumatriptan is a medicine to treat migraines and cluster headaches. It does not prevent these conditions.

It belongs to a group of medicines called triptans, or serotonin (5-HT1) agonists.

You take sumatriptan once a migraine or cluster headache has started. It is not a painkiller but you can use this medicine if painkillers or non-steroidal anti-inflammatory drugs (NSAIDs) have not worked.

Sumatriptan comes as tablets, a nasal spray or injection. The nasal spray and injection are used to treat migraines and cluster headaches. The tablets are used for migraines only.

Sumatriptan tablets, nasal spray and injections are available on prescription. You can also buy packs containing two 50mg tablets from a pharmacy without a prescription, but only if you have previously been diagnosed with migraines.

• Take sumatriptan as soon as a migraine or cluster headache starts.
• The tablets usually work within 30 to 60 minutes. The spray and injection work quicker.
• Common side effects include feeling or being sick, feeling sleepy or dizzy.
• Do not take migraine medicines such as ergotamine or other triptans when taking sumatriptan.
• Sumatriptan is also known by the brand names Imigran, Migraitan and Boots Migraine Relief 50mg Tablets.

Most adults with migraines can have sumatriptan tablets or injections. But the nasal spray is only officially approved for people under the age of 65.

Sumatriptan is not officially approved for children. However, a specialist doctor may sometimes prescribe it for a child over the age of 6 years.

Sumatriptan is not suitable for some people. To make sure it's safe for you, tell your doctor if you:

• have had an allergic reaction to sumatriptan or any other medicine in the past
• have a heart problem such as coronary heart disease, chest pain (angina), heart rhythm problems (arrhythmia) or you've had a heart attack
• have circulation problems in your legs (peripheral vascular disease)
• have had a stroke or "mini stroke" (transient ischaemic attack)
• have liver disease or other liver problems
• have seizures or fits
• are trying to get pregnant, are already pregnant or breastfeeding
• are a heavy smoker or use nicotine replacement therapy (particularly if you've been through menopause, or if you're a man over the age of 40)
• have high blood pressure

You may be able to use sumatriptan if you've had high blood pressure in the past and it is now well controlled with treatment.

Always follow your doctor's instructions when taking this medicine.

Take your first dose as soon as the pain starts.

Do not take it at the warning stage, before your migraine starts. This is when some people get symptoms of "aura".

Tablets (for migraine only)

Swallow the tablet whole with a drink of water. Do not chew or crush it.

If you find tablets difficult to swallow, some come with a line in the middle to help you break them in half. Check the information leaflet inside the medicine packet to see if you can do this with your medicine.

The usual dose is 50mg. But some people may be prescribed 100mg.

The tablets should work in 30 to 60 minutes. If your migraine improves but then comes back, you can take the same dose again after 2 hours.

However, if the first dose of sumatriptan does not help, do not take another dose for the same attack.

Injections (migraine or cluster headache)

Read the instructions that come with your medicine to find out how to use the pre-filled syringe (auto-injector) and how to get rid of it safely afterwards.

Use the pre-filled syringe to inject 1 dose. This contains 6mg of sumatriptan. You'll usually inject it into your thigh.

The medicine generally works in 10 to 15 minutes.

If your headache improves but then comes back, you can inject another dose after 1 hour.

However, if the first sumatriptan injection does not help, do not have another one for the same attack.

Nasal spray (migraine or cluster headache)

Read the instructions that come with your medicine to find out how to use the single-use nasal spray. Each spray contains 1 dose (10mg or 20mg of sumatriptan).

1. Blow your nose if it feels blocked or if you have a cold.
2. Place your finger over 1 nostril.
3. Spray the medicine into the other nostril and breathe in gently at the same time.

The nasal spray usually works within 15 minutes.

If your headache improves but then comes back, you can have another dose after 2 hours.

However if the first dose of sumatriptan does not help, do not take another dose for the same attack.

What if I take too much?

Do not take more than the prescribed amount in any 24-hour period. The maximum amount is 300mg of tablets, 12mg as injections or 40mg as a nasal spray.

Taking too much sumatriptan may make you very ill. An overdose can cause fainting, slowed heart rate, vomiting, loss of bladder and bowel control, and sleepiness.

It can narrow your blood vessels leading to heart problems such as chest pains, abnormal heart rhythm or a heart attack. It can also reduce the blood supply to other organs such as part of your large intestine This can give you a severe stomach ache.

If you need to go to hospital, do not drive yourself. Get someone else to drive you or call for an ambulance.

Take the sumatriptan packet or leaflet inside it plus any remaining medicine with you.

Like all medicines, sumatriptan can cause side effects. However, many people have no side effects or only minor ones.

Common side effects

These common side effects happen in more than 1 in 100 people. They're usually mild and short lived. Some of the side effects are similar to the symptoms of migraine or cluster headaches.

Talk to your doctor or pharmacist if these side effects bother you or last more than a few days:

• feeling or being sick (nausea or vomiting)
• feeling dizzy, unsteady on your feet or tired
• feeling hot or cold, face flushes red

With the nasal spray:

• irritation or burning in your nose or throat
• nosebleeds
• bad taste in your mouth

With the injections:

• bruising or swelling where you gave yourself the injection
• bleeding where you gave yourself the injection

Serious side effects

It happens rarely, but some people have serious side effects when taking sumatriptan.

Do not take any more sumatriptan and tell a doctor straight away if you get continued or increasing:

• tightness or tingling in your face, arms, legs or chest
• unusual feelings of heaviness in your face, arms, legs or chest
• feelings of warmth or cold in your face, arms, legs or chest

These feelings usually don't last for long. If they continue, or become severe or intense, seek medical help straight away.

Serious allergic reaction

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

These are not all the side effects of sumatriptan.

For a full list, see the leaflet inside your medicines packet.

What to do about:

• feeling or being sick (nausea or vomiting) – these side effects may be due to the migraine itself. If you feel able to eat, stick to simple meals and do not eat rich or spicy food. If you're being sick, try small frequent sips of water to avoid dehydration. Signs of dehydration include peeing less than usual or having dark strong-smelling pee.
• feeling dizzy, unsteady on your feet or tired – if you begin to feel dizzy, lie down so that you do not faint, then sit until you feel better. Do not drive or use tools or machines if you feel dizzy or a bit shaky.
• feeling hot or cold, face flushes red – if this bothers you or does no't go away, speak to a GP.
• irritation or burning in your nose or throat – this usually only lasts for a short time.
• nosebleeds – these will usually only last for a short time. Seek immediate medical help if the bleeding does not stop after 10 to 15 minutes, especially if you're taking a blood-thinning medicine such as warfarin or rivaroxaban, or you have haemophilia or any other condition that means your blood cannot clot properly.
• bad taste in your mouth – try chewing sugar-free gum.
• bruising or swelling (where you gave yourself the injection) – this is usually mild and will go away after 1 to 3 days. See a doctor if it gets worse, becomes painful or inflamed or if it lasts for longer than a few days.
• bleeding (where you gave yourself the injection) – this should only last a short time. Seek immediate medical help if the bleeding does not stop after 10 to 15 minutes, especially if you're taking a blood-thinning medicine such as warfarin or rivaroxaban, or you have haemophilia or any other condition that means your blood can't clot properly.

Sumatriptan is not thought to be harmful during pregnancy, but there is not enough research to say for certain.

Talk to a doctor about the benefits and possible harms of taking sumatriptan. There may be other medicines that are safer for you.

Find out more about how sumatriptan can affect you and your baby during pregnancy by Best Use of Medicines in Pregnancy (BUMPS).

Sumatriptan and breastfeeding

It's usually safe to take sumatriptan if you're breastfeeding. Only small amounts of the medicine get into breast milk and so it's not enough to cause any problems for your baby.

However, speak to a doctor if your baby was premature or has any health problems.

There are some medicines that may interfere with the way sumatriptan works.

Tell your doctor before you take sumatriptan if you're already taking:

• other migraine or headache medicines (including ergotamine and other triptans)
• antidepressants called MAOIs (monoamine oxidase inhibitors
• antidepressants

If you're taking antidepressants, check with your doctor whether it's safe to take sumatriptan with your other medicines. Using sumatriptan with some types of antidepressants can increase your risk of a severe side effect called serotonin syndrome.

Symptoms of seretonin sydrome include:

• feeling confused or agitated
• muscle twitching
• high temperature, sweating or shivering
• increased heart rate
• diarrhoea

Tell a doctor immediately if you get any of these symptoms.

Mixing sumatriptan with herbal remedies or supplements

Taking sumatriptan with St John's wort (hypericum perforatum) can increase your risk of serotonin syndrome. Do not take St John's wort if you're using sumatriptan.