Indications

Meclizine is indicated for the prevention and treatment of nausea, vomiting, dizziness, and motion sickness. It is also used for radiation sickness and vertigo associated with diseases of the vestibular system, such as Meniere's syndrome and labyrinthitis.

Pharmacology

Meclizine is a piperazine-derivative antihistamine with antiemetic, anticholinergic, and antihistaminic properties. It works by reducing the sensitivity of the inner ear's balance apparatus (the labyrinthine apparatus). Its effect may be mediated through nerve pathways to the vomiting center from the chemoreceptor trigger zone, peripheral nerve pathways, and other CNS centers. Pyridoxine, or vitamin B6​, is added to enhance the anti-emetic effects and serves as a dietary supplement.

Dosage & Administration

• Adults and Children 12 years of age and over:
  • Nausea and vomiting: 25-50 mg daily.
  • Motion sickness: An initial dose of 25-50 mg should be taken one hour before travel. This dose can be repeated every 24 hours for the duration of the journey.
  • Radiation sickness: 50 mg should be administered 2-12 hours prior to radiation treatment.
  • Vertigo: 25-100 mg daily in divided doses.
  • Emergency contraceptive pill (ECP)-associated nausea/vomiting: 25-50 mg one hour before the first ECP dose, and repeated if needed in 24 hours.
• Children under 12 years of age: Safety and efficacy have not been established.

Interaction

• CNS depressants: The sedative effects of Meclizine can be increased by alcohol or other CNS depressants such as benzodiazepines, barbiturates, tricyclic antidepressants, opiate agonists, skeletal muscle relaxants, and other antihistamines.
• Anticholinergics: Concurrent use of other anticholinergic drugs can potentiate Meclizine's anticholinergic effects.
• Digoxin: Meclizine can increase the absorption of digoxin by decreasing gastrointestinal motility.

Contraindications

This medication is contraindicated in patients who are hypersensitive to meclizine hydrochloride, pyridoxine hydrochloride, or any of the inactive ingredients.

Side Effects

The most commonly reported side effects are drowsiness and dry mouth. Blurred vision has been reported on rare occasions.

Pregnancy & Lactation

Meclizine is classified as Pregnancy Category B. Large-scale human studies have not shown adverse fetal effects. Based on available data, meclizine is considered the lowest risk option and is the drug of first choice for treating nausea and vomiting during pregnancy. Its safety for use in nursing mothers has not been established.

Precautions & Warnings

• Impaired alertness: Patients should be warned that meclizine may impair their ability to perform activities requiring mental alertness or physical coordination, such as driving or operating machinery.
• Alcohol: Patients should avoid alcoholic beverages while taking this medication.
• Underlying medical conditions: Due to its potential anticholinergic action, Meclizine should be used with caution in patients with asthma, glaucoma, or an enlarged prostate gland.

Overdose Effects

Symptoms of overdose can include extreme excitability, seizures, drowsiness, and hallucinations. Treatment is supportive and symptomatic and may involve dialysis.

Therapeutic Class

Meclizine is an anti-emetic drug.

Storage Conditions

Keep below 30°C, away from light and moisture. Keep out of the reach of children.