Flunarizine is a calcium channel blocking agent developed in the 1960s and later introduced into clinical use for the prevention of migraine and the treatment of vestibular disorders such as vertigo. It is structurally related to antihistamines and shows both calcium channel blocking and antihistaminic properties. Its clinical importance lies in its ability to reduce cerebral vascular excitability and stabilize vascular tone, which helps in decreasing the frequency of migraine attacks. Flunarizine became widely used as a prophylactic therapy in patients with recurrent migraines and balance disorders, especially in cases where other treatments were not effective or tolerated.
BRAND NAMES
Common brand names of Flunarizine include:
Sibelium (most widely known international brand)
In some countries, it is also marketed under different local generic brand names as “Flunarizine hydrochloride”
MECHANISM OF ACTION
Flunarizine is a selective calcium channel blocker that reduces calcium influx into vascular smooth muscle and neurons. This leads to stabilization of vascular tone and decreased cerebral vasospasm. It also has antihistaminic and sedative properties, which contribute to its effectiveness in preventing migraines and treating vestibular disorders such as vertigo.
PHARMACOKINETICS
Absorption
Flunarizine is well absorbed orally but undergoes significant first-pass metabolism.
Distribution
It is highly lipophilic and extensively distributed in tissues, including the brain. It is highly protein-bound.
Metabolism
It is metabolized in the liver into inactive metabolites.
Elimination
Elimination is slow, mainly via feces, with a long half-life (several days), allowing once-daily dosing.
PHARMACODYNAMICS
Flunarizine reduces excessive neuronal excitability and stabilizes vascular smooth muscle tone. It is mainly used for:
Migraine prophylaxis
Vertigo and vestibular disorders
Prevention of cerebral ischemia-related symptoms (in some cases)
ADMINISTRATION
It is given orally, usually once daily at night due to its sedative effects.
DOSAGE AND STRENGTH
Typical adult dose is low (commonly 5–10 mg daily), adjusted based on response and tolerability.
DRUG INTERACTIONS
Flunarizine may enhance the effects of sedatives, alcohol, and CNS depressants, leading to increased drowsiness. It may also interact with antiepileptic drugs.
FOOD INTERACTIONS
No major food interactions are known, but alcohol should be avoided due to additive sedation.
CONTRAINDICATIONS
Depression or history of severe depression
Parkinson’s disease (can worsen symptoms)
Hypersensitivity to the drug
SIDE EFFECTS
Drowsiness and sedation
Weight gain
Fatigue
Depression (important adverse effect)
Extrapyramidal symptoms (rare, especially in elderly)
OVER DOSAGE
Overdose of flunarizine is uncommon but can occur due to excessive intake or accumulation (because of its long half-life and high tissue binding). The main effects are related to central nervous system depression and extrapyramidal symptoms.
TOXICITY
Overdose of Flunarizine may cause excessive sedation, hypotension, bradycardia, and severe central nervous system depression. In some cases, extrapyramidal symptoms such as tremors or parkinsonism-like features may appear.
