Zolmitriptan

Migraines are complex physiological events characterized by unilateral throbbing headaches combined with photophobia and other aversions to sensory input. Migraine attacks are generally divided into phases: the premonitory phase, which typically involves irritability, fatigue, yawning, and stiff neck; the headache phase, which lasts for between four and 72 hours; and the postdrome phase, which lasts for up to a day following resolution of pain and whose symptoms are similar to those of the premonitory phase. In addition, neurological deficits, collectively termed migraine aura, may precede the headache phase.

The underlying pathophysiology of migraines is a matter of active research but involves both neurological and vascular components. The head pain associated with migraine is thought to be a consequence of activation of the nociceptive nerves comprising the trigeminocervical complex (TCC). Terminals of nociceptive nerves that innervate the dura matter release vasoactive peptides, such as calcitonin gene-related peptide (CGRP), resulting in cranial vasodilation. Finally, when present, migraine aura appears to correlate with a transient wave(s) of cortical depolarization, termed cortical spreading depression (CSD).

Triptans, including zolmitriptan, are proposed to act in three ways. The main mechanism is through modulation of nociceptive nerve signalling in the central nervous system through 5-HT1B/1D receptors throughout the TCC and associated areas of the brain. In addition, triptans can enhance vasoconstriction, both through direct 5-HT1B-mediated dilation of cranial blood vessels, as well as through 5-HT1D-mediated suppression of CGRP release.

Although triptans are classically described solely in terms of their effects on 5-HT1B/1D receptors, they also act as 5-HT1F agonists as well. This 5-HT subtype is also found throughout the TCC, but is not present appreciably in cerebral vasculature; the significance of triptan-mediated 5-HT1F activation is currently not well described. Additionally, CSD that initiates in the ipsilateral parietal region may exert its effects in a manner that relies on 5-HT1B/1D receptor activation, suggesting that triptans may have some effect on CSD-mediated symptoms.