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.