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Meclizine is an antihistamine considered to be an antiemetic. It is sold under the brand names of Bonine, Bonamine, Antivert, Postafen, Sea Legs, and Dramamine (Less Drowsy Formulation). Emesafene is a combination of meclizine (1/3) and pyridoxine (2/3). In Canada, Antivert Tab (which is no longer available) was a combination of meclizine and nicotinic acid.
Classification
Meclizine is a first-generation antihistamine of the piperazine class. Meclizine is structurally and pharmacologically similar to buclizine, cyclizine, and hydroxyzine. It is used as an antivertigo/antiemetic agent, specifically, in the prevention and treatment of nausea, vomiting, and dizziness associated with motion sickness.
Mechanism of Action
Meclizine is an antagonist at H1-receptors. It possesses anticholinergic, central nervous system depressant, and local anesthetic effects. Its antiemetic and antivertigo effects are not fully understood, but its central anticholinergic properties are partially responsible. The drug depresses labyrinth excitability and vestibular stimulation, and it may affect the medullary chemoreceptor trigger zone.
Uses
Meclizine is FDA approved to treat symptoms of motion sickness and for management of vertigo that stems from diseases affecting the vestibular system. Meclizine's safety and efficacy in children younger than 12 years old has not been established, therefore use in this population is not recommended. Also, meclizine should be taken with caution in the elderly (greater than 65 years old) because of increased risk of confusion and amnesia.
Motion sickness
Meclizine is effective in inhibiting the symptoms of motion sickness, such as nausea, vomiting, and dizziness. The recommended dose is 25-50 mg orally, taken 1 hour before travel. The dose may be repeated every 24 hours as needed.
Vertigo
Meclizine may be effective in relieving vertigo experienced as a result of inner ear infections or other conditions. The recommended dose is 25-100 mg per day orally, separated into divided doses.
Side Effects
Some common side effects such as drowsiness, dry mouth, and tiredness may occur. Meclizine has been shown to have less dry mouth side effects than the traditional treatment for motion sickness, transdermal scopolamine. A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching/swelling, severe dizziness, and/or trouble breathing.
Drowsiness
Drowsiness may result as a side effect of taking meclizine. Users are advised not to operate heavy machinery while under the influence. The consumption of alcohol while under the influence of meclizine may result in additional drowsiness.
Special Considerations in the Elderly
As with any anticholinergic agent, meclizine may cause confusion or aggravate symptoms in those with dementia in the geriatric population (those greater than 65 years of age). Therefore caution should be used when administering meclizine to the elderly.
Dahl E, Offer-Ohlsen D, Lillevold PE, Sandvik L. Transdermal scopolamine, oral meclizine, and placebo in motion sickness. Clinical Pharmacology And Therapeutics 1984 Jul; Vol. 36 (1), pp. 116-20. Available from: MEDLINE: Ipswich, MA. PMID 6734040
