Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


Chemistry - Meclizine HCl is a piperazine derivative antiemetic antihistamine.

Storage, Stability, Compatibility

Meclizine products should be stored at room temperature inwell-closed containers.

Pharmacology - MECLIZINE HCL

Meclizine is a piperazine antihistamine and beside its antihistamine activity, it alsopossesses antiemetic, CNS depressant, antiemetic, antispasmodic and local anesthetic effects. Theexact mechanism of action for its antiemetic and anti-motion-sickness effects are not completelyunderstood, but it is thought they are as a result of the drug's central anticholinergic and CNSdepressant activity. The antiemetic effect is probably mediated through the chemoreceptor triggerzone (CTZ).

Uses, Indications

Meclizine is principally used in small animals as an antiemetic and for thetreatment and prevention of motion sickness.

Pharmacokinetics - MECLIZINE HCL

Very little information is available. Meclizine is metabolized in the liver andhas a serum half life of about 6 hours.

Contraindications, Precautions, Reproductive Safety

Meclizine is contraindicated in patientshypersensitive to it. It should be used with caution in patients with prostatic hypertrophy, bladderneck obstruction, severe cardiac failure, angle-closure glaucoma or pyeloduodenal obstruction.
Meclizine is considered to be teratogenic in animals. Cleft palates have been noted in rats at 25-50times higher than labeled dosages. It should be used during pregnancy only when the potentialbenefits outweigh the risks. It is unknown if it enters maternal milk and its anticholinergic activitymay potentially inhibit lactation.

Adverse Effects, Warnings

The usual adverse effect noted with meclizine is sedation; less frequently anticholinergic effects may be noted (dry mucous membranes, eyes, tachycardia, etc.).
Contradictory CNS stimulation has also been reported.
Overdosage, Acute Toxicity - Moderate overdosage may result in drowsiness alternating withhyperexcitability. Massive overdosages may result in profound CNS depression, hallucinations, seizures and other anticholinergic effects (tachycardia, urinary retention, etc.). Treatment is considered symptomatic and supportive. Consider gut emptying when patients present soon after ingestion. Avoid respiratory depressant medications.

Drug Interactions

Use with other CNS depressants may cause additive sedation. Other anticholinergic drugs may cause additive anticholinergic effects.
Laboratory Considerations - Because these drugs are antihistamines, they may affect the resultsof skin tests using allergen extracts. Do not use within 3-7 days before testing.

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