meclizine

Has central anticholinergic, CNS depressant, and antihistaminic properties.
Decreases excitability of the middle ear labyrinth and depresses conduction in middle ear vestibular-cerebellar pathways.

Therapeutic effects:

Decreased motion sickness.
Decreased vertigo from vestibular pathology.

Pharmacokinetics ⬆ ⬇

Absorption: Absorbed after oral administration.

Distribution: Unknown.

Metabolism/Excretion: Primarily metabolized by liver via the CYP2D6 isoenzyme; the CYP2D6 isoenzyme exhibits genetic polymorphism (∼7% of population may be poor metabolizers and may have significantly ↑ meclizine concentrations and an ↑ risk of adverse effects).

Half-Life: 6 hr.

Time/Action Profile ⬆ ⬇

(antihistaminic effects)

ROUTE	ONSET	PEAK	DURATION
PO	1 hr	unknown	8–24 hr

Contraind./Precautions ⬆ ⬇

Contraindicated in:

Hypersensitivity.

Use Cautiously in:

Prostatic hyperplasia;
Angle-closure glaucoma;
Lactation: Use while breastfeeding only if potential maternal benefit justifies potential risk to infant;
Pedi: Children 12 yr (safety and effectiveness not established);
Geri: Appears on Beers list. risk of anticholinergic adverse reactions in older adults, including falls, delirium, and dementia. Avoid use in older adults.

Adv. Reactions/Side Effects ⬆ ⬇

EENT: blurred vision

GI: dry mouth

Neuro: drowsiness, fatigue

Interactions ⬆ ⬇

Drug-drug:

Additive CNS depression with other CNS depressants, including alcohol, other antihistamines, opioid analgesics, and sedative/hypnotics.
Additive anticholinergic effects with other drugs possessing anticholinergic properties, including some antihistamines, antidepressants, atropine, haloperidol, phenothiazines, quinidine, and disopyramide.
CYP2D6 inhibitors may ↑ levels and risk of toxicity

Route/Dosage ⬆ ⬇

PO (Adults and Children ≥12 yr): Motion sickness: 25–50 mg 1 hr before exposure; may repeat in 24 hr; Vertigo: 25–100 mg/day in divided doses.

Availability ⬆ ⬇

(Generic available)

Tablets: 12.5 mg; 25 mg^{Rx, OTC}; 50 mg
Chewable tabletsraspberry flavor: 25 mg^OTC

Assessment ⬆ ⬇

Assess patient for level of sedation after administration.
Motion Sickness: Assess patient for nausea and vomiting before and 60 min after administration.
Vertigo: Assess degree of vertigo periodically in patients receiving meclizine for labyrinthitis.

Lab Test Considerations:

May cause false-negative results in skin tests using allergen extracts. Discontinue meclizine 72 hr before testing.

Implementation ⬆ ⬇

PO: Administer oral doses with food, water, or milk to minimize GI irritation. DNC: Swallow tablets whole; do not crush, break, or chew.
- Chewable tablets must be chewed or crushed completely before swallowing. Do not swallow chewable tablets whole.

Patient/Family Teaching ⬆ ⬇

Instruct patient to take meclizine exactly as directed. If a dose is missed, take as soon as possible unless almost time for next dose. Do not double doses.
- May cause drowsiness. Caution patient to avoid driving or other activities requiring alertness until response to the medication is known.
- Advise patient that frequent mouth rinses, good oral hygiene, and sugarless gum or candy may decrease dryness of mouth.
- Caution patient to avoid concurrent use of alcohol and other CNS depressants, including opioids, with this medication.
- Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected, or if breastfeeding.
Motion Sickness: When used as prophylaxis for motion sickness, advise patient to take medication at least 1 hr before exposure to conditions that may cause motion sickness.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇