Meclizine

Meclizine Uses, Dosage, Side Effects, Food Interaction and all others data.

Meclizine has antiemetic, anticholinergic and antihistaminic properties. It reduces the sensitivity of the labyrinthine apparatus. The action may be mediated through nerve pathways to the vomiting center (VC) from the chemoreceptor trigger zone (CTZ), peripheral nerve pathways, the VC, or other CNS centers. Meclizine has an onset of action of 30 to 60 minutes, depending on dosage; their duration of action is 12 to 24 hours.

Meclizine works on the higher centres of the brain to reduce nausea, vomiting, or vertigo. It is effective against nausea and vomiting arising from many causes, including motion sickness and disorders affecting the vestibular system. The onset of action of meclizine is about 1 hour, with effects lasting between 8 to 24 hours. Meclizine is reported to cause drowsiness due to its anticholinergic actions.

Trade Name Meclizine
Availability Rx and/or OTC
Generic Meclizine
Meclizine Other Names Meclizine, Meclozina, Meclozine
Related Drugs hydroxyzine, lorazepam, ondansetron, Zofran, promethazine, diphenhydramine, Benadryl, Phenergan, scopolamine, dimenhydrinate
Type
Formula C25H27ClN2
Weight Average: 390.948
Monoisotopic: 390.186276581
Protein binding

There is limited data on the protein binding profile of meclizine.

Groups Approved
Therapeutic Class Anti-emetic drugs
Manufacturer
Available Country United States
Last Updated: September 19, 2023 at 7:00 am
Meclizine
Meclizine

Uses

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

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

How Meclizine 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. Meclizine may also decrease the labyrinth excitability and vestibular stimulation.

Dosage

Meclizine 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 Meclizine (like other antiemetics) with caution.

Interaction

Meclizine 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.

Meclizine 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.

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

Meclizine 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

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

Pregnancy & Breastfeeding use

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

Contraindication

Meclizine is contraindicated in patients hypersensitive to Meclizine 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

You find simplified version here Meclizine

Meclizine contains Meclizine see full prescribing information from innovator Meclizine Monograph, Meclizine MSDS, Meclizine FDA label

*** Taking medicines without doctor's advice can cause long-term problems.
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