cyclizine hydrochloride
Marezine

cyclizine lactate
Marezine, Marzine ◆

Available forms
Available with or without a prescription
cyclizine hydrochloride
Tablets: 50 mg
cyclizine lactate
Injection: 50 mg/ml

Indications and dosages
 Motion sickness (prophylaxis and treatment). Adults and children older than age 12: 50 mg P.O. (hydrochloride) 30 minutes before travel, then q 4 to 6 hours, p.r.n., to maximum of 200 mg daily; or 50 mg I.M. (lactate) q 4 to 6 hours, p.r.n.
Children ages 6 to 12: 25 mg P.O. up to t.i.d. under medical supervision.

Pharmacodynamics
Antiemetic action: Probably inhibits nausea and vomiting by centrally depressing sensitivity of the labyrinth apparatus that relays stimuli to the chemoreceptor trigger zone and thus stimulates the vomiting center in the brain.
Antivertigo action: Depresses conduction in vestibular-cerebellar pathways and reduces labyrinth excitability.

Pharmacokinetics
Absorption: Not well characterized; onset of action between 30 and 60 minutes.
Distribution: Well distributed throughout body.
Metabolism: Metabolized in liver.
Excretion: No information available; drug effect lasts 4 to 6 hours or 12 to 24 hours depending on dosage.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug. Use cautiously in patients with heart failure, BPH, asthma, or recent surgery.

Interactions
Drug-drug. Aminoglycosides, cisplatin, loop diuretics, salicylates, vancomycin: May mask signs of ototoxicity. Don’t give together.
CNS depressants (such as anxiolytics, barbiturates, sleeping aids, tranquilizers): Causes additive sedative and CNS depressant effects. Monitor patient closely.
Drug-lifestyle. Alcohol use: Causes additive sedative and CNS depressant effects. Discourage alcohol use.

Adverse reactions
CNS: drowsiness, auditory and visual hallucinations, restlessness, excitation, nervousness.
CV: hypotension, palpitations, tachycardia.
EENT: blurred vision, diplopia, tinnitus, dry nose and throat.
GI: constipation, dry mouth, anorexia, nausea, vomiting, diarrhea, cholestatic jaundice.
GU: urine retention, urinary frequency.
Skin: urticaria, rash.

Effects on lab test results
None reported.

Overdose and treatment
Signs and symptoms of overdose may include either CNS depression (sedation, reduced mental alertness, apnea, and CV collapse) or CNS stimulation (insomnia, hallucinations, tremors, or seizures). Anticholinergic symptoms, such as dry mouth, flushed skin, fixed and dilated pupils, and GI symptoms, are common, especially in children.
 Treat overdose with gastric lavage to empty stomach contents; inducing emesis with ipecac syrup may be ineffective. Treat hypotension with vasopressors, and control seizures with diazepam or phenytoin. Don’t give stimulants.

Special considerations
• Injectable cyclizine is for I.M. use only. When giving I.M., aspirate and check carefully for blood return; inadvertent I.V. administration can cause anaphylaxis.
• Injectable solution is incompatible with many drugs; check compatibility before mixing in same syringe.
• Store in a cool place; at room temperature, injection may turn slightly yellow but doesn’t lose its potency.
• Cyclizine may prevent, reduce, or mask response to diagnostic skin testing. Stop cyclizine 4 days before diagnostic skin testing to avoid altered test response.
Breast-feeding patients
• Antihistamines such as cyclizine shouldn’t be used during breast-feeding. Most appear in breast milk, exposing infant to risks of unusual excitability; premature infants are at particular risk for seizures. Cyclizine also may inhibit lactation.
Pediatric patients
• Drug isn’t indicated for use in children younger than age 6; they may experience paradoxical hyperexcitability. Safety and efficacy of I.M. administration in children haven’t been established and use isn’t recommended. Geriatric patients
• Elderly patients are usually more sensitive to adverse effects of antihistamines and are more likely than younger patients to experience dizziness, sedation, hyperexcitability, dry mouth, and urine retention.

Patient education
• Instruct patient to stay in places of minimal motion (such as in middle, not front or back, of ship), avoid excessive intake of food or drink, and not to read while in motion.
• Tell patient to avoid hazardous activities requiring mental alertness until CNS reaction is determined.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use