Flunarizine is a selective calcium channel blocker of the diphenylpiperazine class, with potent cerebral and peripheral vasodilatory properties. It is a fluorinated derivative of cinnarizine. Its primary clinical utility in India is for the prophylaxis of migraine and management of vestibular vertigo. It acts by inhibiting calcium influx into vascular smooth muscle cells and neurons, reducing vasospasm and neuronal hyperexcitability. It also exhibits antihistaminic and antidopaminergic properties.
Adult: For Migraine Prophylaxis: 10 mg (two 5mg tablets) once daily at bedtime for initial therapy. Maintenance: After 2 months, may reduce to 5 mg once daily at bedtime if effective. For Vertigo: 10 mg daily at bedtime for acute control, reducing to 5 mg daily for maintenance.
Note: Administer orally, preferably at bedtime to minimize daytime drowsiness. Can be taken with or without food. Swallow the tablet whole with a glass of water. Do not crush or chew.
Flunarizine exerts its therapeutic effects through multiple mechanisms: 1) Selective blockade of voltage-gated T-type calcium channels in vascular smooth muscle and neuronal cells, preventing calcium influx. This leads to cerebral vasodilation and reduced vasospasm. 2) Inhibition of calcium overload in hypoxic cells, providing a cytoprotective effect. 3) Antagonism of dopamine D2 receptors in the chemoreceptor trigger zone (CTZ), contributing to its anti-vertigo and anti-emetic effects. 4) Antagonism of histamine H1 receptors, contributing to its sedative and vestibular suppressant properties.
Pregnancy: Category C: Animal studies have shown teratogenic effects. There are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus. Avoid especially in the first trimester.
Driving: STRONGLY DISCOURAGED, especially during initiation and dose adjustment. Can cause drowsiness, dizziness, and blurred vision, impairing the ability to drive or operate machinery.
| CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Potentiated sedation, drowsiness, impaired motor skills. | Major |
| Antipsychotics (Haloperidol, Risperidone) | Increased risk of extrapyramidal symptoms (EPS) and hyperprolactinemia. | Major |
| Antidepressants (SSRIs, TCAs) | Increased risk of serotonin syndrome (theoretical) and additive CNS effects. | Moderate |
| Strong CYP2D6 Inhibitors (Paroxetine, Fluoxetine) | May increase flunarizine plasma levels, increasing toxicity risk. | Moderate |
| Antihypertensives | Potential additive hypotensive effect. | Moderate |
| Levodopa | Flunarizine may antagonize the therapeutic effect of levodopa in Parkinson's disease. | Major |