Meclozine

Uses

Meclozine Hydrochloride is used for nausea, vomiting, motion sickness, vertigo.

Meclozine is also used to associated treatment for these conditions: Dizziness, Motion Sickness

How Meclozine works

Vomiting is a centrally regulated reflex mechanism that initiates from the vomiting center and the chemoreceptor trigger zone (CTZ) located in the medulla. Motion sickness is also regulated by CTZ. The blood-brain barrier near the CTZ is relatively permeable to circulating mediators and CTZ can transmit impulses to vomiting center located in the brainstem. Different receptors responding to different factors, including histamine, 5-HT, enkephalins, substance P, and dopamine, are expressed along the brainstem to activate respective pathways and contribute to the control of vomiting. Histamine H1 receptors are expressed on the vestibular nuclei and nucleus of the solitary tract (NTS) that are activated by motion sickness and stimuli from the pharynx and stomach. When activated, H1 receptor signaling from these nuclei is transmitted to the CTZ and vomiting centre.

Through its antagonistic action on the H1 receptors, meclizine primarily works by inhibiting signaling pathway transduction through histaminergic neurotransmission from the vestibular nuclei and NTS to the CTZ and medullary vomiting center. Meclozine may also decrease the labyrinth excitability and vestibular stimulation.

Dosage

Meclozine dosage

Adult & children over 12 years of age:

• Nausea and vomiting: 25-50 mg once daily.
• Motion sickness: Take an initial dose of 25 to 50 mg, 1 hour prior to travel. May repeat dose every 24 hours for the duration of the journey.Children: Age 6-12 years, 12.5 mg once daily. Age 2-6 years, 6.25 mg once daily.
• Vertigo: 25 to 100 mg daily in divided doses.
• Radiotherapy induced nausea and vomiting: 50 mg two to twelve hours prior to radiotherapy.
• Emergency contraception: 25-50 mg, 1 hour before first ECP dose; repeat if needed in 24 hours.

Use in children: Clinical studies establishing safety and efficacy in children have not been done; therefore, its use should be determined by physician.

Use in elderly: There is no specific information available. However older people may be especially sensitive to the anticholinergic effects of medicine.

Side Effects

Common side effects are Drowsiness, dry mouth, and on rare occasions, blurred vision have been reported.

Toxicity

The oral and intraperitoneal LD₅₀ in mouse are 1600 mg/kg and 625 mg/kg, respectively. The lowest published toxic dose (TDLo) in rats via the oral route is 800 mg/kg.

Symptoms of overdose mainly involve CNS depression with drowsiness, coma, and convulsions. Hypotension may also occur, particularly in the elderly. In children, anticholinergic effects and CNS stimulation, characterized by hallucinations, seizures, trouble sleeping, are more likely to occur. In case of overdose, symptomatic and supportive treatment is recommended. In case of recent ingestion, induction of emesis or gastric lavage should be initiated to limit further drug absorption. Although there is no known antidote to meclizine, physostigmine may be useful to counteract the CNS anticholinergic effects of meclizine.

Precaution

Patients with asthma, bronchitis, emphysema, enlarged prostate, glaucoma or urinary tract blockage should take Meclozine (like other antiemetics) with caution.

Interaction

Meclozine may increase the toxicity with CNS depressants, neuroleptics and anticholinergic. Alcohol, sedatives and tranquilizers can increase the drowsiness of the patient.

Food Interaction

• Avoid alcohol. Alcohol may cause additive CNS depressant effects.

Meclozine Alcohol interaction

[Moderate] GENERALLY AVOID:

Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous.

In addition, the potential for abuse may be increased with the combination.

The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system.

No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load.

However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

Alcohol should generally be avoided during therapy with anticholinergic agents.

Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.

Meclozine Drug Interaction

Moderate: diphenhydramine, duloxetine, pregabalin, acetaminophen / hydrocodone, alprazolam, cetirizineUnknown: aspirin, omega-3 polyunsaturated fatty acids, fluticasone nasal, metoprolol, polyethylene glycol 3350, esomeprazole, albuterol, montelukast, levothyroxine, acetaminophen, cyanocobalamin, ascorbic acid, cholecalciferol, ondansetron

Meclozine Disease Interaction

Moderate: anticholinergic effects, asthma/COPD, cardiovascular, renal/liver disease

Volume of Distribution

The volume of distribution of meclizine in humans has not been fully studied. It is proposed that meclizine may be excreted into breast milk.

Elimination Route

Most histamine H1 antagonists are reported to be readily absorbed following oral administration. Upon oral administration, the time to reach peak plasma concentrations (Cmax) of meclizine is about 3 hours post-dose, with the value ranging from 1.5 to 6 hours.

Half Life

Meclozine has a plasma elimination half-life of about 5-6 hours in humans.

Clearance

There is limited data on the clearance of meclizine.

Elimination Route

Meclozine is excreted in the urine as metabolites and in the feces as unchanged drug.

Pregnancy & Breastfeeding use

Meclozine shows no risk of birth defects or abnormalities when administered during pregnancy. Although Meclozine may excrete into the milk, it causes no harm in nursing babies.

Contraindication

Meclozine is contraindicated in patients hypersensitive to Meclozine or any of its excipeints.

Acute Overdose

Symptoms: Extreme excitability, seizures, drowsiness and hallucinations.

Treatment: Appropriate supportive and symptomatic treatment. Consider dialysis.

Storage Condition

Store in a cool & dry place and away from children.

Innovators Monograph

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