Eletriptan

Eletriptan Hydrobromide is the active metabolite of Relpax®, the only FDA-approved eletriptan product currently on the market in the U.S. Eletriptan is a second generation triptan drug developed by Pfizer Inc for the treatment of migraine headaches.

Approval and availability
Relpax was approved by the U.S. FDA on December 26, 2002 for the acute treatment of migraine with or without aura in adults. It is available only by prescription in the United States and Canada. It is not intended for the prophylactic therapy of migraine or for use in the management of hemiplegic or basilar migraine. It is available in 20 mg and 40 mg strengths.

Relpax tablets for oral administration contain 24.2 mg or 48.5 mg of eletriptan hydrobromide equivalent to 20 mg or 40 mg of eletriptan, respectively. Each tablet also contains the inactive ingredients microcrystalline cellulose NF, lactose NF, croscarmellose sodium NF, magnesium stearate NF, titanium dioxide USP, hydroxypropyl methylcellulose NF, triacetin USP and FD&C Yellow No. 6 aluminum lake.

Mode of action
Treatment with Relpax reduces swelling of blood vessels surrounding the brain. This swelling is associated with the headache pain of a migraine attack. Relpax blocks the release of substances from nerve endings that cause more pain and other symptoms like nausea, and sensitivity to light and sound. It is thought that these actions contribute to relief of symptoms by Relpax.

Eletriptan is a serotonin agonist. Specifically, it is a selective 5-hydroxytryptamine 1B/1D (5-HT1B/1D) receptor agonist.

Eletriptan binds with high affinity to 5-HT1B, 5-HT1D and 5-HT1F receptors, has modest affinity for 5-HT1A, 5-HT1E, 5-HT2B and 5-HT7 receptors, and little or no affinity for 5-HT2A, 5-HT2C, 5-HT3, 5-HT4, 5-HT5A and 5-HT6 receptors. Eletriptan has no significant affinity or pharmacological activity at adrenergic alpha1, alpha2, or beta; dopaminergic D1 or D2; muscarinic; or opioid receptors.

Two theories have been proposed to explain the efficacy of 5-HT receptor agonists in migraine. One theory suggests that activation of 5-HT1 receptors located on intracranial blood vessels, including those on the arteriovenous anastomoses, leads to vasoconstriction, which is correlated with the relief of migraine headache. The other hypothesis suggests that activation of 5-HT1 receptors on sensory nerve endings in the trigeminal system results in the inhibition of pro-inflammatory neuropeptide release.

Chemical name: (R)-5-[2-(Fenylsulfonyl)etyl]-3-[(1-metyl-2-pyrrolidinyl)metyl]-1H-indol