Three distinct pharmacological actions have been implicated in the antimigraine effect of the triptans: (1) stimulation of presynaptic 5-HT1D receptors, which serves to inhibit both dural vasodilation and inflammation; (2) direct inhibition of trigeminal nuclei cell excitability via 5-HT1B/1D receptor agonism in the brainstem and (3) vasoconstriction of meningeal, dural, cerebral or pial vessels as a result of vascular 5-HT1B receptor agonism.

Rizatriptan is a selective agonist of serotonin (5-hydroxytryptamine; 5-HT) type 1B and 1D receptors. It is structurally and pharmacologically related to other selective 5-HT1B/1D receptor agonists and has only a weak affinity for 5-HT_1A, 5-HT_5A, and 5-HT₇ receptors and no significant affinity or pharmacological activity at 5-HT₂, 5-HT₃ or 5-HT₄ receptor subtypes or at alpha1-, alpha2-, or beta-adrenergic, dopamine1, ; dopamine2; muscarinic, or benzodiazepine receptors. This action in humans correlates with the relief of migraine headache. In addition to causing vasoconstriction, experimental data from animal studies show that Rizatriptan also activates 5-HT₁ receptors on peripheral terminals of the trigeminal nerve innervating cranial blood vessels, which may also contribute to the antimigrainous effect of Rizatriptan in humans.

Rizatriptan is metabolized by monoamine oxidase A isoenzyme (MAO-A) to an inactive indole acetic acid metabolite. In addition, several other inactive metabolites are formed. An active metabolite, N-monodesmethyl-rizatriptan, with pharmacological activity similar to that of the parent compound has been identified in small concentrations (14%) in the plasma.

Symptoms of overdose include dizziness, fainting, heart and blood vessel problems, high blood pressure, loss of bowel and bladder control, slow heartbeat, and vomiting.

1. Wellington K, Plosker GL: Rizatriptan: an update of its use in the management of migraine. Drugs. 2002;62(10):1539-74. [PubMed:12093318 ]
2. Wellington K, Jarvis B: Spotlight on rizatriptan in migraine. CNS Drugs. 2002;16(10):715-20. [PubMed:12269863 ]
3. Ikemoto F, Toru T, Aijima H, Natsumeda Y: [Rizatriptan (Maxalt), a new entity of triptan for migraine: pharmacology and therapeutic relevance]. Nihon Yakurigaku Zasshi. 2004 Apr;123(4):295-302. [PubMed:15056946 ]
4. Villalon CM, Centurion D, Valdivia LF, De Vries P, Saxena PR: An introduction to migraine: from ancient treatment to functional pharmacology and antimigraine therapy. Proc West Pharmacol Soc. 2002;45:199-210. [PubMed:12434581 ]
5. Tfelt-Hansen P, De Vries P, Saxena PR: Triptans in migraine: a comparative review of pharmacology, pharmacokinetics and efficacy. Drugs. 2000 Dec;60(6):1259-87. [PubMed:11152011 ]