Imitrex is the first of a class of medications commonly referred to as the "triptans". It is a specific medication for aborting migraine headaches. It is also effective in cluster headache as an abortive medication. It appears to act in migraine by binding to selected receptors for serotonin found in the blood vessels (5HT1b) and nerve endings (5HT1d). By binding to these receptors it keeps the migraine from developing or causes it to end. It does not appear to stop migraine auras.
Sumatriptan has been available in the United States since 1993. Formulations include a self-administered injection given under the surface of the skin (subcutaneous), nasal spray or oral tablets. In 2004, the tablets were reformulated to dissolve more quickly in the stomach. They are still swallowed as a conventional tablet, not an orally dissolving product. The injectable form is very rapid in its onset of action and can stop a migraine in 15 minutes in some patients. The oral form is slower and usually reaches its maximum effect within two hours. The nasal spray is somewhere between the other two in the amount of time it takes to begin working.
The injectable form contains 6 mg of sumatriptan. Doses should not be taken closer than one hour apart and then only if the first dose provided at least partial relief. Generally, it should not be used more than two days per week. Side effects are common with this form of sumatriptan only because of how rapidly the medication enters the system. In most people, the side effects (i.e., a sensation of warmth, scalp, neck or chest tightness, and/or lightheadedness) pass very quickly and are not severe.
The oral form comes in 25 mg, 50 mg and 100 mg tablets. The dose can be repeated after 2 hours. A maximum of 200 mg should be taken in any 24-hour period. While few patients require only 25 mg to stop a migraine, 50 mg and 100 mg are more effective. A physician can guide you to determine the most effective dose for you.
The nasal spray is available in 5 mg and 20 mg per dose units. Both doses were effective in clinical trials, but practical use of these forms is still limited. As with the injectable form, both the oral and nasal spray forms should be used no more than two days per week. Side effects with both of these other forms are much less common and severe than the injectable. Triptans can be effective if taken at any time after the headache develops but provide pain-free relief best when taken early in the headache, while the pain is still mild.
The triptans need to be used with caution, if at all, in patients who have complicated forms of migraine such as basilar migraine or hemiplegic migraine. The same is true for patients who have poorly controlled high blood pressure. Patients who have cardiovascular, cerebrovascular or peripheral vascular disease affecting the blood vessels should not use this medication. Patients with risk factors such as high cholesterol, diabetes or high blood pressure may need further testing before using triptans.