Imigran (Imitrex) injection is indicated for the acute relief of migraine attacks with or without aura, and for the acute treatment of cluster headache.
Administration
Imigran injection should not be used prophylactically.
It is recommended to start the treatment at the first sign of a migraine headache or associated symptoms such as nausea, vomiting or photophobia. The efficacy of sumatriptan is independent of the duration of the attack when starting treatment. Administration during a migraine aura prior to other symptoms occurring may not prevent the development of a headache.
Imigran injection should be injected subcutaneously using an autoinjector.
Patients should be advised to observe strictly the instruction leaflet for the Imigran autoinjector, especially regarding the safe disposal of syringes and needles.
Migraine
The recommended adult dose of Imigran injection is a single 6mg subcutaneous injection.
If a patient does not respond to the first dose of Imigran, a second dose should not be taken for the same attack. Imigran injection may be taken for subsequent attacks.
If the patient has responded to the first dose, but the symptoms recur a second dose may be given in the next 24 hours, provided that there is a minimum interval of one hour between the two doses.
The maximum dose in 24 hours is two 6mg injections (12mg).
Cluster Headache
The recommended adult dose of Imigran Injection is a single 6mg subcutaneous injection for each cluster attack. The maximum dose in 24 hours is two 6mg injections (12mg) with a minimum interval of one hour between the two doses.
Children (under 18 years of age)
The safety and effectiveness of sumatriptan in children has not yet been established.
Elderly (over 65)
Experience of the use of sumatriptan in patients aged over 65 years is limited. The pharmacokinetics do not differ significantly from a younger population, but until further clinical data are available, the use of sumatriptan in patients aged over 65 years is not recommended.
Contra-Indications
Hypersensitivity to any component of the preparation.
Sumatriptan should not be given to patients who have had a myocardial infarction or have ischaemic heart disease (IHD), Prinzmetal's angina/coronary vasospasm, peripheral vascular disease or patients who have symptoms or signs consistent with IHD.
Sumatriptan should not be administered to patients with a history of previous cerebrovascular accident (CVA) or transient ischaemic attack (TIA).
The use of sumatriptan in patients with uncontrolled hypertension is contraindicated.
Sumatriptan should not be administered to patients with severe hepatic impairment.
The concomitant use of ergotamine or derivatives of ergotamine (including methysergide) is contraindicated (see Interaction with Other Medicaments and Other Forms of Interaction).
Concurrent administration of monoamine oxidase inhibitors (MAOIs) and sumatriptan is contraindicated. Sumatriptan must not be used within two weeks of discontinuation of therapy with monoamine oxidase inhibitors.
Special Warnings and Special Precautions for Use
Imigran injection should only be used where there is a clear diagnosis of migraine or cluster headache.
Imigran injection should not be given intravenously.
Sumatriptan is not indicated for use in the management of hemiplegic, basilar or ophthalmoplegic migraine.
As with other acute migraine therapies, before treating headaches in patients not previously diagnosed as migraineurs, and in migraineurs who present with atypical symptoms, care should be taken to exclude other potentially serious neurological conditions. It should be noted that migraineurs may be at increased risk of certain cerebrovascular events (eg. cerebrovascular accident, transient ischaemic attack).
Following administration, sumatriptan can be associated with transient symptoms including chest pain and tightness which may be intense and involve the throat (see Undesirable Effects). Where such symptoms are thought to indicate ischaemic heart disease appropriate evaluation should be carried out.
Sumatriptan should not be given to patients in whom unrecognised cardiac disease is likely without a prior evaluation for underlying cardiovascular disease. Such patients include postmenopausal women, males over 40 and patients with risk factors for coronary artery disease.
However, these evaluations may not identify every patient who has cardiac disease and, in very rare cases, serious cardiac events have occurred in patients without underlying cardiovascular disease.
Sumatriptan should be administered with caution to patients with controlled hypertension as transient increases in blood pressure and peripheral vascular resistance have been observed in a small proportion of patients.
There have been rare postmarketing reports describing patients with weakness, hyper-reflexia, and incoordination following the use of a selective serotonin reuptake inhibitor (SSRI) and sumatriptan. If concomitant treatment with sumatriptan and an SSRI is clinically warranted, appropriate observation of the patient is advised (see Interaction with Other Medicaments and Other Forms of Interaction).
Sumatriptan should be administered with caution to patients with conditions which may affect significantly the absorption, metabolism or excretion of the medicine, eg. impaired hepatic or renal function.
Sumatriptan should be used with caution in patients with a history of seizures or other risk factors which lower the seizure threshold.
Patients with known hypersensitivity to sulphonamides may exhibit an allergic reaction following administration of sumatriptan. Reactions may range from cutaneous hypersensitivity to anaphylaxis. Evidence of cross sensitivity is limited, however, caution should be exercised before using sumatriptan in these patients.
The recommended dose of Imigran should not be exceeded.
Pregnancy and Lactation
Caution should be exercised by considering the expected benefit to the mother against possible risk to the foetus.
Post-marketing data from multiple prospective pregnancy registries have documented the pregnancy outcomes in over 1,000 women exposed to sumatriptan. Although there is insufficient information to draw definitive conclusions, the findings have not detected an increase in the frequency of birth defects nor a consistent pattern of birth defects, amongst women exposed to sumatriptan compared with the general population.
No teratogenic effects have been seen in rats or rabbits and sumatriptan had no effect on the post-natal development of rats.
When administered to pregnant rabbits throughout the period of organogenesis sumatriptan has occasionally caused embryolethality at doses which were sufficiently high to produce maternal toxicity.
It has been demonstrated that following subcutaneous administration sumatriptan is excreted into breast milk. Infant exposure can be minimised by avoiding breast feeding for 12 hours after treatment.
Effects on Ability to Drive and Operate Machinery
Drowsiness may occur as a result of migraine or its treatment with sumatriptan.
Caution is recommended in patients performing skilled tasks, eg. driving or operating machinery.
Interaction with other medicaments and other forms of interaction
There is no evidence of interactions with propanolol, flunarizine, pizotifen or alcohol.
Prolonged vasospastic reactions have been reported with ergotamine. As these effects may be additive, 24 hours should elapse before sumatriptan can be taken following any ergotamine containing preparation. Conversely, ergotamine containing preparations should not be taken until 6 hours have elapsed following sumatriptan administration.
An interaction may occur between sumatriptan and MAOIs and concomitant administration is contraindicated (see Contraindications). Rarely an interaction may occur between sumatriptan and SSRIs (see Special Warnings and Special Precautions for Use).
Undesirable Effects
Adverse events are listed below by system organ class and frequency. Frequencies are defined as: very common (>1/10), common (>1/100, <1/10), uncommon (>1/1000, <1/100), rare (>1/10,000, <1/1000) and very rare (<1/10,000) including isolated reports. The data from clinical trials are estimates. It should be noted that the background rate in comparator groups was not taken into account. Post-marketing data refer to reporting rate rather than true frequency.
CLINICAL TRIAL DATA
Nervous System Disorders
Common: Tingling, dizziness, drowsiness.
Vascular disorders
Common: Transient increases in blood pressure arising soon after treatment. Flushing.
Gastrointestinal
Common: Nausea and vomiting occurred in some patients but the relationship to sumatriptan is not clear.
Musculoskeletal and Connective Tissue Disorders
The following symptom is usually transient and may be intense and can affect any part of the body including the chest and throat:
Common: Sensations of heaviness.
General Disorders and Administration Site Conditions
The following symptoms are usually transient and may be intense and can affect any part of the body including the chest and throat:
Common: Pain, sensations of heat, pressure or tightness.
The following symptoms are mostly mild to moderate in intensity and transient:
Common: Feelings of weakness, fatigue.
Injection
The most common side effects associated with treatment with Imigran administered subcutaneously are:
Very common: Transient injection site pain.
Injection site stinging/burning, swelling, erythema, bruising and bleeding have also been reported.
Although direct comparisons are not available, flushing and sensations of tingling, heat, pressure, and heaviness may be more common after Imigran injection.
Conversely, nausea, vomiting and fatigue appear to be less frequent with subcutaneous administration of Imigran injection than with tablets.
POST-MARKETING DATA
Immune System Disorders
Very rare: Hypersensitivity reactions ranging from cutaneous hypersensitivity to rare cases of anaphylaxis.
Nervous System Disorders
Very rare: Seizures, although some have occurred in patients with either a history of seizures or concurrent conditions predisposing to seizures there are also reports in patients where no such predisposing factors are apparent.
Tremor, dystonia, nystagmus, scotoma.
Eye disorders
Very rare: Flickering, diplopia, reduced vision. Loss of vision (usually transient). However, visual disorders may also occur during a migraine attack itself.
Cardiac Disorders
Very rare: Bradycardia, tachycardia, palpitations, cardiac arrhythmias, transient ischaemic ECG changes, coronary artery vasospasm, myocardial infarction (see Contraindications, Warnings and Precautions).
Vascular Disorders
Very rare: Hypotension, Raynaud's phenomenon.
Gastrointestinal
Very rare: Ischaemic colitis.
Overdose
There have been some reports of overdosage with Imigran Injection.
Patients have received single injections of up to 12mg subcutaneously without significant adverse effects. Doses up to 16mg subcutaneously were not associated with side effects other than those mentioned.
If overdosage occurs, the patient should be monitored for at least ten hours and standard supportive treatment applied as required.
It is unknown what effect haemodialysis or peritoneal dialysis has on the plasma concentrations of sumatriptan.
Pharmacological Properties
Sumatriptan has been demonstrated to be a selective vascular 5-hydroxytryptamine-1-(5HT1D) receptor agonist with no effect at other 5HT receptor (5HT2 -5HT7) subtypes. The vascular 5HT1D receptor is found predominantly in cranial blood vessels and mediates vasoconstriction.
In animals sumatriptan selectively constricts the carotid arterial circulation, but does not alter cerebral blood flow. The carotid arterial circulation supplies blood to the extracranial and intracranial tissues such as the meninges and dilatation and/or oedema formation in these vessels is thought to be the underlying mechanism of migraine in man. In addition, experimental evidence suggests that sumatriptan inhibits trigeminal nerve activity. Both these actions may contribute to the anti-migraine action of sumatriptan in humans.
Clinical response begins 10-15 minutes following a 6mg subcutaneous injection, and around 30 minutes following a 100mg oral dose.
Pharmacokinetic Properties
The pharmacokinetics of oral sumatriptan do not appear to be significantly affected by migraine attacks.
Incompatibilities
None reported.
Shelf Life
24 months.
Storage
Imigran Injection should be stored below 30°C or 86°F, protected from light.
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