Pizotifen is a tricyclic compound. It antagonizes serotonin receptor competitively. It possesses antihistamine, antibradykinin and weak anticholinergic properties. It also possesses appetite-stimulating properties.

Pharmacology

Pizotifen works by inhibiting the peripheral actions of serotonin and histamine in increasing the membrane permeability of cranial vessels and transudation of plasmakinin, while altering pain thresholds in migraines. By blocking 5-HT receptors, pizotifen attenuates the signalling of serotonin in causing cranial vasoconstriction, as well as serotonin-enhanced platelet function and aggregation. There is evidence that it also inhibits the peripheral actions of bradykinin. Pizotifen may inhibit serotonin reuptake by blood platelets, which affects the tonicity and decreases passive distension of extracranial arteries. The effects of pizotifen leading to appetite stimulation may be due to the drug acting at the metabolic level rather than a direct stimulation of the appetite centre.

Pizotifen is indicated as prophylactic treatment of vascular headache of migraine type such as classical migraine, common migraine and cluster headache. It is not effective in relieving migraine attacks once in progress.

Adults: Usually 1.5 mg daily. This may be taken as a single dose at night or in three divided doses. Dosage should be adjusted to the individual patient requirements up to a maximum of 4.5 mg daily. Up to 3 mg may be given as a single dose.

Children (aged over 2 years): Up to 1.5 mg daily, usually as a divided dose, although up to 1 mg has been given as a single dose at night.

Pizotifen is contraindicated in patients with known hypersensitivity to any of its ingredients.

The most common side effects are appetite stimulating effect, increase in body weight and drowsiness.

Urinary retention, renal impairment should be taken in consideration. Drowsiness may affect the performance driving vehicles & operation of machineries. Pizotifen enhances the action of alcohol.

Pregnancy & Lactation

Information of using Pizotifen in pregnancy is limited, although no ill effects have been reported. The drug should therefore only be given during pregnancy if the potential benefit to mother justifies the potential risk to the fetus. The safety of Pizotifen during lactation has not been established, so mothers should avoid taking it when breast feeding.