| Indication |
For the acute treatment of migraine attacks with or without aura in adults. |
| Pharmacodynamics |
Naratriptan 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
agonist. Naratriptan has only a weak affinity for 5-HT1A, 5-HT5A, 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 Naratriptan 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
Naratriptan in humans. |
| Mechanism of action |
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. |
| Absorption |
Well absorbed (74% oral biovaility), absorption is rapid with peak
plasma concentrations after 2-5 hours. The rate of absorption is slower
during a migraine attack. |
| Volume of distribution |
|
| Protein binding |
28%-31% (over the concentration range of 50 to 1000 ng/mL) |
| Metabolism |
Primarily hepatic. In vitro, naratriptan is metabolized by a wide range of cytochrome P450 isoenzymes into a number of inactive metabolites. |
| Route of elimination |
Not Available |
| Half life |
5-8 hours |
| Clearance |
|
| Toxicity |
Symptoms of overdose include light-headedness, loss of coordination, tension in the neck, and tiredness. |
