Triptans

The triptans, a class of serotonin receptor agonists, have carved out a significant niche in the pharmacologic management of vascular headaches and migraine. Their unique mechanism of action and generally favorable safety profile make them an essential component in the therapeutic arsenal against these debilitating headaches.

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Triptan - indole structure

Mechanism of Action

Serotonin, scientifically termed as 5-hydroxytryptamine (5-HT), is a monoamine neurotransmitter that boasts a myriad of functions. Its actions span across neurotransmission and as a bioactive amine, thereby affecting various physiological processes. The complexity of serotonin's effects largely arises from its vast array of receptors and their distinct tissue distributions. To date, researchers have identified at least 15 classes of serotonin receptors, each characterized by different intracellular pathways responding variably to stimulation and inhibition.

Triptans are specifically synthesized to be serotonin agonists that exhibit a pronounced affinity for the 5-HT1B and 5-HT1D receptors. These receptors are predominantly located on the smooth muscle cells lining blood vessels. Activating the 5-HT1D receptor, in particular, leads to the constriction of intracranial blood vessels. Additionally, triptans might inhibit the release of vasoactive peptides from perivascular trigeminal neurons, owing to their influence on presynaptic 5-HT1D receptors on nerve endings. Collectively, these actions underline the efficacy of triptans in either aborting or preventing migraine headaches, facilitating the reduction in the duration of pain and associated symptoms. When conventional analgesics fail to provide consistent relief from vascular headaches, triptans emerge as the "first line" therapeutic agents. Their rapid onset of action and reduced side effects, compared to ergot alkaloids, further enhance their clinical utility.

Liver Safety

Although triptans are typically administered in small doses over short durations, their hepatotoxicity profile remains largely benign. There have been no prominent associations between triptans and elevations in serum enzymes. However, rare instances of acute cholestatic hepatitis have been reported following their administration.

Available Triptans

The United States has sanctioned the use of seven triptans:

• Almotriptan
• Eletriptan
• Forvatriptan
• Naratriptan
• Rizatriptan
• Sumatriptan
• Zolmitriptan

With most of these agents available in generic forms, they can be broadly classified based on their duration of action. The fast-acting triptans, like sumatriptan, almotriptan, eletriptan, rizatriptan, and rolmitriptan, typically confer relief within 30 to 60 minutes post-administration. On the other hand, naratriptan and frovatriptan, the long-acting oral triptans, possess a more delayed onset but might be better tolerated. The intranasal forms of these drugs might ensure a quicker therapeutic effect, akin to their subcutaneously administered counterparts.

Recommendations for individuals with recurrent migraines emphasize the importance of early intervention. If the initial dose fails to provide relief, it may be repeated after an interval of 2 to 4 hours. However, the cumulative dose should not exceed 2 to 3 administrations within a 24-hour timeframe. To cater to patients plagued by nausea and vomiting, parenteral and intranasal routes of administration might be preferable. Although studies have probed into the long-term prophylactic use of triptans for migraine prevention, no approvals for such indications currently exist.

Adverse Effects

Across the spectrum of available triptans, the adverse effect profile remains fairly consistent. Commonly termed "triptan sensations," these side effects manifest as a constriction sensation in the throat, chest, neck, and limbs, accompanied by paresthesias and temperature variations. Other potential side effects encompass flushing, headache, drowsiness, and fatigue. While rare, some severe adverse reactions linked with triptans include:

• Medication overuse syndrome
• Cerebrovascular and cardiovascular incidents like myocardial infarction and stroke
• Serotonin syndrome
• Anaphylactic reactions

Patients and clinicians should remain vigilant about these potential side effects, especially when using triptans as a primary therapeutic intervention for vascular headaches and migraines.

Triptans Resources
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