Meclizine is a first-generation piperazine-derivative antihistamine (H1-receptor antagonist) with pronounced antimuscarinic and central nervous system depressant properties. It is primarily used for the prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness and vertigo of various etiologies. Its efficacy stems from its ability to suppress labyrinthine excitability and depress conduction in the vestibular-cerebellar pathways.
Adult: For Motion Sickness: 25-50 mg orally, 1 hour before travel. May repeat 24-hourly if required. For Vertigo: 25-100 mg daily in divided doses, as per physician's advice. Typical maintenance: 25 mg three times daily.
Note: Administer orally with or without food. For motion sickness prophylaxis, take at least 1 hour before anticipated travel. Tablet can be broken for dose titration. Advise adequate hydration.
Meclizine competitively antagonizes histamine H1 receptors in the central nervous system, particularly in the vestibular apparatus and the chemoreceptor trigger zone (CTZ). It also possesses significant anticholinergic (antimuscarinic) activity. This dual action reduces the sensitivity of the labyrinthine apparatus, inhibits the vestibular-cerebellar pathways, and diminishes the excitability of the CTZ, thereby alleviating nausea, vomiting, and dizziness.
Pregnancy: Category B (US FDA). Animal studies show no risk, but no adequate controlled studies in pregnant women. Use only if clearly needed, preferably after the first trimester. Avoid in early pregnancy unless potential benefit justifies potential risk.
Driving: STRONGLY DISCOURAGED. Can cause significant drowsiness and impair cognitive and motor skills. Patients should not drive or operate heavy machinery until their individual response is known.
| Alcohol, Benzodiazepines, Opioids | Potentiation of CNS depression, leading to severe drowsiness, impaired coordination, and respiratory depression. | Major |
| Other Anticholinergics (e.g., Atropine, TCAs, Antipsychotics) | Additive anticholinergic side effects (dry mouth, constipation, urinary retention, confusion). | Major |
| CNS Depressants (Barbiturates, Sedative Hypnotics) | Increased sedative effect. | Moderate |
| Monoamine Oxidase Inhibitors (MAOIs) | Exaggerated anticholinergic and CNS depressant effects. | Contraindicated |
| CYP2D6 Inhibitors (e.g., Fluoxetine, Paroxetine, Quinidine) | May increase meclizine plasma levels, increasing risk of side effects. | Moderate |
Same composition (Meclizine (25mg)), different brands: