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The Difference Between Imitrex and Relpax

The Difference Between Imitrex and Relpax


One of the most commonly encountered causes of a headache is an acute migraine attack. This affects 30 million people in the United States and about 325 million worldwide. According to epidemiologic estimates, this illness is four times more common among women in their early adulthood. People suffering from migraine attacks generally experience a throbbing headache that can be felt on one or both sides of the head. The pain intensity of migraine headaches may vary from moderate to severe, and headaches can be accompanied by other symptoms, such as nausea and vomiting. People who suffer from migraine attacks also report sensitivity to light and sound; these stimuli were observed to trigger severe exacerbation of symptoms upon exposure. Typically, migraine headaches last for several hours, and, in severe cases, disabling headaches can last for several days.

The cause of headaches in migraine attacks can be attributed to abnormalities of the blood vessels in the brain. According to brain specialists, cerebral blood vessels are widened and inflamed during an acute attack. Known triggering factors, such as loud sound, flashes of light, anxiety, and hormonal imbalance, may precipitate dilation of blood vessels in the brain, initiating events that lead to migraine headaches. Although the exact cause and mechanism of migraine headaches are still unknown, current evidence shows that migraines are a neurovascular disease.

Treatments for Migraines

At present, several medications are available for migraine attacks. However, the first-line medications that are usually prescribed by clinicians belong to a group of drugs called Serotonin 1B/1D agonists. They are more commonly called “Triptans” because these drugs have the suffix “–triptan” in their nomenclature. Triptans relieve headaches in a migraine attack by narrowing blood vessels in the brain. They enhance the activity of serotonin, a neurohormone and a neurotransmitter that causes constriction of the vessel walls. Triptans also control blood vessel inflammation by inhibiting the release of inflammatory molecules in the central nervous system. Two of the commonly used prescribed triptans are Sumatriptan and Eletriptan, which are marketed as Imitrex and Relpax respectively. In this article, we will discuss the difference between both medications.

Sumatriptan (Imitrex)

Sumatriptan is the prototype of serotonin agonists that was made available on the market for the treatment of migraines. Because of this, it is referred to as the first-generation triptan. This drug comes in many formulations, and it can be administered orally, via nasal inhalation, skin injection, or application of a skin patch. Sumatriptan is an analog of serotonin, which causes activation of serotonin receptors that are located in the blood vessels of the brain. These are called 5-HT 1B/1D receptors, which are specific for the brain. Sumatriptan does not activate other serotonin receptors, and it also does not have any affinity for other neutrotransmitter receptors in the brain. Because of this, Sumatriptan is able to relieve migraine headaches through vascular constriction and control of inflammatory molecules. The formulation of Sumatriptan, which has the fastest onset of action, is via subcutaneous injection, which takes effect within 15 minutes of drug administration. In comparison to orally and intranasally prepared formulations, which are expected to take effect within a range of 20 minutes to an hour. The peak of headache relief can be achieved within a period of two hours for intranasal and subcutaneously injected formulations, while orally administered Sumatriptan has a peak clinical effect after four hours from the time of drug administration.

Eletriptan (Relpax)

Eletriptan (Relpax) is the most recently marketed serotonin agonist for migraines. Compared to Sumatriptan, Eletriptan is considered a second-generation triptan, together with Naratriptan, Rizatriptan, Zolmitriptan, and Frovatriptan. It is only available in an oral formulation, whereas Sumatriptan can be administered by several routes. However, its oral bioavailability is better than Sumatriptan, enabling it to have a faster time to achieve a peak clinical effect on relief of pain. After oral administration of Eletriptan, peak effect is expected to be noticeable within 90 minutes, compared to Sumatriptan, which has the earliest peak of action within 2 hours after drug administration. Moreover, Eletriptan is metabolized in the liver by a specific enzyme called, cytochrome P3A4. Several drugs, such as Ketocoazole, Itraconazole, Ritonavir, and Clarithromycin, inhibit this enzyme. Because of these, Eletriptan cannot be co-administered with these medications in order to avoid unwanted side effects. Several research studies show that Eletriptan has a comparable clinical efficacy to Sumatriptan in pain relief during acute migraine attacks, making it a popular treatment choice for migraines.


Both Sumatriptan (Imitrex) and Eletriptan (Relpax) can be used to relieve headaches in an acute migraine attack. Sumatriptan is available in several drug formulations and can be administered orally, intranasally, or through skin injection. On the other hand, Eletriptan is only available in an oral formulation. Despite this, Eletriptan carries the advantage of having an earlier peak of action at 90 minutes than Sumatriptan. Eletriptan is metabolized by cytochrome P3A4, which is why it should not be administered with medications that interfere with its enzymatic activity. Both medications are equally effective, and treatment selection is usually based on individual responses to these medications for acute migraine attacks.

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References :

[0]Brucker, M., & King, T. (2017). Pharmacology for women's health (2nd ed.). Burlington, MA: Jones & Bartlett Learning.

[1]Capi, M., Curto, M., Lionetto, L., de Andrés, F., Gentile, G., Negro, A., & Martelletti, P. (2016). Eletriptan in the management of acute migraine: an update on the evidence for efficacy, safety, and consistent response. Therapeutic Advances in Neurological Disorders, 9(5), 414–423. http://doi.org/10.1177/1756285616650619

[2]Lehne, R. A. (2013). Pharmacology for nursing care. St. Louis, MO: Elsevier/Saunders.

[3]Rosenberg, R. N. (2009). Atlas of clinical neurology. Philadelphia, PA: Springer/Current Medicine Group.

[4]Tfelt-Hansen, P., Vries, P. D., & Saxena, P. R. (2000). Triptans in Migraine. Drugs, 60(6), 1259-1287. doi:10.2165/00003495-200060060-00003


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