Imigran subject (Sumatriptan)

How does it work?

Imigran subject injection contains the active ingredient sumatriptan, which is a type of medicine called a serotonin (or 5HT) agonist. This type of medicine is also commonly known as a triptan. It is a painkiller specifically used to relieve migraine attacks.

Although the cause of migraine attacks is not fully understood, it is thought that widening of blood vessels in the brain causes the throbbing pain of migraine headaches. Sumatriptan relieves this pain by causing the blood vessels in the brain to narrow.

Sumatriptan works by stimulating receptors called serotonin (or 5HT) receptors that are found in the brain. A natural substance called serotonin normally acts on these receptors, causing blood vessels in the brain to narrow. Sumatriptan mimics this action of serotonin by directly stimulating the serotonin receptors in the brain. This narrows the blood vessels and so relieves the pain of migraine headaches.

The dose of sumatriptan should be taken as early as possible after the migraine headache has started, though it is also effective if taken at a later stage during the migraine attack.

Imigran subject is an injection that is administered under the skin (subcutaneously) to relieve migraine attacks or cluster headaches. The medicine starts to work at relieving the headache within about 10 to 15 minutes after the injection is given. It may be particularly useful for people who feel sick or vomit during their headache, as the medicine is not taken by mouth.

What is it used for?

  • Relieving migraine attacks.
  • Relieving cluster headaches.


  • This medicine should not be used to prevent migraines or cluster headaches.
  • This medicine should only be used by people with a clear diagnosis of migraine or cluster headache from their doctor.
  • Carefully follow the instructions provided with your Imigran subject injections. DO NOT administer the injection into a vein. If you do not understand or are unsure about anything, ask your doctor or pharmacist for advice.
  • If your first dose of this medicine doesn't relieve your migraine headache then you should NOT take another dose for the same attack, as trials have shown that this is not effective. However, if the first dose does initially relieve your migraine headache but the headache then comes back, a second dose can be effective. If you need a second dose because your migraine has returned, you should NOT take it within one hour of your first dose. Do not exceed the recommended dose. Do not use more than two 6mg injections (12mg) in any 24 hour period.
  • Consult your doctor if your migraine doesn't go away, or if you have frequent or daily headaches. It is important not to use this medicine too frequently, because taking a painkiller for headaches or migraines too often or for too long can actually make the headaches worse.
  • This medicine can cause feelings of warmth, heaviness, pressure, tightness or pain in certain parts of the body, including the chest or throat. Although sometimes very strong, these feelings usually only last a few minutes. If they continue or are particularly severe (especially chest pain), you should tell your doctor immediately, as there have been extremely rare reports of such problems being caused by a heart attack. Do NOT use another dose; your doctor will decide if you should stop using this medicine.
  • This medicine may cause drowsiness. If affected do not drive or operate machinery.

Use with caution in

  • Allergy to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole.
  • Controlled high blood pressure (hypertension).
  • People with risk factors for ischaemic heart disease, such as smoking, high cholesterol levels, diabetes, obesity, or a family history of heart disease.
  • Men over 40 years.
  • Postmenopausal women.
  • Decreased kidney function.
  • Decreased liver function.
  • History of seizures eg epilepsy, or people with conditions that increase the risk of seizures, eg head injury, alcoholism.

Not to be used in

  • People who have had a heart attack.
  • Heart disease caused by inadequate blood flow to the heart (ischaemic heart disease), eg angina.
  • A severe form of angina pectoris, not caused by exertion (Prinzmetal's angina).
  • Narrowing of blood vessels in the extremities, eg legs (peripheral vascular disease).
  • History of stroke.
  • History of small temporary temporary strokes (transient ischaemic attacks).
  • Uncontrolled or moderate to severe high blood pressure (hypertension).
  • Severely decreased liver function.
  • People who have taken a monoamine-oxidase inhibitor antidepressant (MAOI) in the last 14 days.
  • A form of migraine associated with paralysis of the eye muscles (ophthalmoplegic migraine).
  • A form of migraine associated with temporary paralysis of one side of the body (hemiplegic migraine).
  • A type of migraine where there is a disturbance in brain function which initially presents with total blindness followed by dizziness, speach disturbances, ringing in the ears and double vision (basilar migraine).
  • Imigran subject is not recommended for children or adolescents aged under 18 years, or adults aged over 65 years, as the safety and efficacy of the injection have not been established in these age groups. Adolescents aged 12-17 years can be treated with Imigran nasal spray, but only on the recommendation of a specialist or doctor with particular experience in migraine. See the factsheet on Imigran nasal spray (linked at the end of this page) for more information.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • The safety of this medicine during pregnancy has not been established. It should only be used by pregnant women if the expected benefit to the mother is greater than any possible risk to the developing baby. Seek medical advice from your doctor.
  • This medicine passes into breast milk. It should be used with caution by breastfeeding mothers. Exposure of the baby to the medicine can be minimised by not breastfeeding for 12 hours following a dose. Discard any breast milk you express in this time. Seek further medical advice from your doctor.

Label warnings

  • Follow the printed instructions you have been given with this medication.
  • This medication may cause drowsiness. If affected do not drive or operate machinery.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Pain, stinging, burning, swelling, redness, bruising or bleeding at the injection site.

Common (affect between 1 in 10 and 1 in 100 people)

  • Sensation of tightness, pressure, tingling, heaviness, heat or pain in any part of the body, including the chest and throat (see warning above).
  • Flushing.
  • Increase in blood pressure.
  • Shortness of breath.
  • Dizziness.
  • Drowsiness.
  • Weakness.
  • Fatigue.
  • Nausea and vomiting (though these may also be due to the migraine).

Very rare (affect less than 1 in 10,000 people)

  • Visual disturbances such as flickering, reduced vision, double vision or loss of vision (though these may also be due to the migraine).
  • Tremor.
  • Seizures.
  • Stiff neck.
  • Increased or decreased heart rate (tachycardia or bradycardia).
  • Awareness of your heart beat (palpitations).
  • Irregular heart beats.
  • Chest pain
  • Heart attack.
  • Alteration in results of liver function tests.
  • Narrowing of the blood vessels in the hands leading to periods of white, painful hands (Raynaud's phenomenom).
  • Low blood pressure (hypotension).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

This medicine must not be taken at the same time as, or within two weeks of taking a monoamine oxidase inhibitor (MAOI), for example, the antidepressants phenelzine, tranylcypromine, isocarboxazid and moclobemide, and the antibiotic linezolid. This is because these medicines could increase the blood level of sumatriptan and therefore increase the risk of side effects.

This medicine must not be used in combination with any other triptan medicines, eg zolmitriptan, eletriptan, naratriptan.

This medicine must not taken within 24 hours of taking ergotamine or its derivatives, eg dihydroergotamine or methysergide. These medicines should not be taken within six hours of taking sumatriptan.

If your first dose of sumatriptan does not work to relieve your migraine, it is fine to take a painkiller containing aspirin, paracetamol, or a non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen. However, as noted above, you should not take ergotamine, dihydroergotamine or methysergide for at least six hours after taking sumatriptan.

There may be an increased risk of a rare side effect called the serotonin syndrome if sumatriptan is taken in combination with other medicines that enhance the activity of serotonin in the central nervous system, such as the following:

  • selective serotonin reuptake inhibitor antidepressants (SSRIs), such as citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine or sertraline
  • serotonin noradrenaline reuptake inhibitors (SNRIs), such as venlafaxine or duloxetine
  • the herbal remedy St John's wort (Hypericum perforatum).

If you are taking any of these medicines you should let your doctor know if you experience symptoms such as confusion, agitation, tremor, muscle twitching, shivering, sweating, racing heartbeat or diarrhoea after taking sumatriptan.

Other medicines containing the same active ingredient

Imigran nasal spray Imigran recovery Imigran tablets

Sumatriptan tablets are also available without a brand name, ie as the generic medicine.