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 ⬆ ⬇

Motion Sickness

PO (Adults and Children ≥12 yr): 25–50 mg 1 hr before exposure; may repeat in 24 hr.

Vertigo

PO (Adults and Children ≥12 yr): 25–100 mg/day in divided doses.

Availability ⬆ ⬇

(Generic available)

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

Assessment ⬆ ⬇

Assess patient for level of sedation after administration.
Motion Sickness: Assess 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 ⬆ ⬇

Explain purpose and side effects of medication to patient. Advise patient to read Patient Information before starting therapy. Instruct patient to take as directed. If a dose is missed, take as soon as possible unless almost time for next dose. Do not double doses.
Advise patient to notify health care provider of all Rx or OTC medications, vitamins, or herbal products being taken and to consult health care provider before taking other medications.
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 ↓ dryness of mouth.
Caution patient to avoid concurrent use of alcohol and other CNS depressants, including opioids, with this medication.
Rep: Advise women of reproductive potential to notify health care provider if pregnancy is planned or suspected or if breastfeeding.
Motion Sickness: When used as prophylaxis for motion sickness, advise patient to take medication >1 hr before exposure to conditions that may cause motion sickness.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇