Introduction

Imitrex is an FDA-approved medication for migraines and tension headaches. Off-label, use includes abortive management of cyclic vomiting syndrome. The active component is sumatriptan succinate. It is a sulfonamide triptan. It is an agonist at serotonin receptors (5-HT1B, 1D) bringing about vasoconstriction and reduction of neuronal inflammation. Currently, three formulations are available in the market: Oral, intranasal, and subcutaneous. It has been associated with several serious side effects key among them being cerebrovascular accidents and myocardial infarctions.

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Description

A sulfonamide triptan that works to reduce neuronal inflammation and bring about vasoconstriction of intracranial blood vessels. This is achieved by agonist action on selective serotonin receptors (5-HT1B, 1D) in the sensory nerve fibers of the trigeminal system and intracranial blood vessels. It prevents the release of vasoactive peptides. 

Available as intranasal, oral, and subcutaneous formulations. The subcutaneous formulation with the most rapid onset of action at 10 minutes as compared to the oral formulation with 30 mins. The intranasal formulation ranges from 15-to 30 minutes. Bio-availability for the subcutaneous formulation at 97% compared to 15% for oral formulations.

Metabolism is hepatic for the most part. It is metabolized to an inactive indole acetic acid metabolite which then undergoes glucuronide conjugation. It can be metabolized by a Monoamine Oxidase enzyme. Oral intake of the drug is followed by first-passing metabolism. 

Peak serum concentrations were achieved in about  2 or 2.5 hours for oral, 5-23 minutes in intranasal sprays, and 4-20 minutes for subcutaneous formulations respectively. 

Excretion is mainly via urine with majority being in the glucuronidated indole acetic acid form. Hepatic impairment can increase the bioavailability of the drug significantly. 

Administration

Intranasal formulations are administered with the Xsail device. Administered to the contralateral nostril in case of cluster headache. You should not breathe deeply.

Care should be taken when administering the drug subcutaneously so as not to deliver the substance to the muscle or in the blood vessel. It must therefore be injected in areas in the body with adequate skin and/or subcutaneous thickness. There were options for implementing auto injector devices. The procedure must be made by a trained health professional. 

Oral formulations should be taken with fluids. The tablet should not be split. The concentration is not uniform throughout the tablet. 

Always remember to follow physician or manufacturer directives.

Use

There are two labeled uses of sumatriptan, 

Acute cluster headaches can be managed with monotherapy of sumatriptan or in combination with 100% oxygen.

With migraine headaches, it can be used as a combination with naproxen. Naproxen inhibits prostaglandins synthesis which are the chemicals involved in the chemical transmission of pain. The naproxen/sumatriptan combination is only in tablet form of 60/10 and 500/85. The combination can be used for migraines acute moderate to severe with or without auras. 

Off-label use includes the abortive treatment of cyclic vomiting syndrome which is often associated with migraines.

Adverse reactions

There are several serious side effects that every physician and patient taking the drug should be aware of.

Use has been associated with cardiac arrhythmias, especially prolonged QT wave abnormalities that can lead to torsades de pointes and ventricular fibrillation. This risk is mainly associated with the use of other drugs that can cause arrhythmias. This is in particular dangerous as it can cause death. Hence females greater than 65 years which had arrhythmias must be managed cautiously or alternatives sought. 

Cardiac events had been experienced. This was owing to vasoconstriction in coronary arterial blood vessels.  These cardiac events were; coronary artery vasospasms, acute myocardial infarctions, takotsubo cardiomyopathy, and cardiac arrests. It was also implicated in the hypertensive crises.

Cerebrovascular events include hemorrhagic strokes, subarachnoid hemorrhages, and ischemic strokes. Potentiated by the taking of estrogen-based contraceptives and being a smoker. 

The CNS’s effects include dizziness, asthenia or drowsiness, tremor, vertigo, akathisia, and dystonia. These effects are dose-dependent because it crosses the blood-brain barrier. 

Ocular effects include total blindness, partial blindness, and angle-closure glaucoma. 

Serotonin syndrome especially when used with other serotonin agonists.

Other side effects include reactions at the injection site, tingling sensations, dizziness, nausea, and vomiting among others.

Interactions

Other drugs can potentiate the side effects associated with sumatriptan. It was advisable to avoid these drugs. They include

No conclusive evidence currently on the potential for congenital malformations during pregnancy.

It crosses into breast milk. Breastfeeding must be withheld in 12 hours after maternal dosing.

Dosage

For adults. Considering adults, subcutaneous dosage is at 6mg per one dose with a repeat dose not within an hour. Care should be taken so as not to exceed a maximum daily dose of 12mg.

Oral formulations come in tablets of 25, 50, and 100mg. The daily dose should not exceed 200 mg and a single dose should not be more than 100mg.

Dosing Considerations

All formulations are contraindicated in severe hepatic impairment. The drug is metabolized by the liver. However significant amounts undergo extrahepatic metabolism. In mild to moderate hepatic impairment, the drug dose should not exceed 50 mg per single oral dose. This applies to both adult and pediatric populations. 

There are no strict dosage adjustments in kidney impairment due to the extensive metabolism of inactive components. 

Information given by the physician and the manufacturer should be followed to avoid serious side effects.

Remember

Follow your physician’s advice and call for immediate help if faced with side effects. Do not use the drug if you are concurrently using MAO-A inhibitors or if using another triptan. Avoid if you currently have or had a history of myocardial infarction, uncontrolled hypertension, arrhythmias, or cerebrovascular events. Be on the lookout for side effects of the drug and seek help if or when they occur. Cease use of the drug if you start experiencing symptoms of an allergic reaction.