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Meclizine

Editor: Yuvraj S. Chowdhury Updated: 2/28/2024 5:33:43 PM

Indications

FDA-Approved Indications

Meclizine, an FDA-approved drug, is a first-generation antihistamine used for the symptomatic management of motion sickness. These symptoms include dizziness, nausea, and vomiting. Meclizine also treats vertigo symptoms caused by vestibular diseases commonly affecting the inner ear, such as Meniere disease.[1][2] 

According to the guidelines by the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), meclizine is a suitable option for managing Meniere disease. Meclizine effectively suppresses vertigo and nausea symptoms commonly associated with Meniere's disease.[3] 

Off-Label Uses

According to the AAO-HNS, meclizine can be used off-label for managing benign paroxysmal positional vertigo (BPPV).[4] Meclizine off-label can also be an option to treat the same symptoms caused by viral illnesses, gastrointestinal infections, pregnancy, or radiation therapy.[5]

Meclizine is also used off-label for managing acute attacks of vestibular migraine.[6] A case report describes the withdrawal symptoms in a 30-year-old woman after discontinuing transdermal scopolamine for motion sickness. Upon patch removal, she experienced persistent and severe nausea, which was alleviated by oral meclizine. Meclizine proved effective in managing withdrawal symptoms without further recurrence of symptoms.[7] 

Achondroplasia is associated with activating mutations in the FGFR3 gene. Meclizine hydrochloride has demonstrated the ability to inhibit FGFR3 signaling and promote bone growth in an animal model of achondroplasia. Phase 1a clinical trial results have shown the safety and achievement of steady-state plasma concentrations of meclizine. In a subsequent phase 1b study involving children with achondroplasia, a 14-day repeated dose of meclizine was well-tolerated without serious adverse events. However, further research is required to confirm the safety and effectiveness of meclizine for managing achondroplasia.[8][9]

Mechanism of Action

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Mechanism of Action

Meclizine is a first-generation antihistamine (non-selective H1 antagonist). The drug also has central anticholinergic actions. The blocking actions on these receptors give meclizine its antiemetic and antivertigo properties. This blocking effect occurs in the medulla's vomiting center and chemoreceptor trigger zone (CTZ).[10] These effects result in the inhibition of signals through histamine neurotransmission from the nucleus of the solitary tract and the vestibular nuclei to the chemoreceptor trigger zone and vomiting center located in the medulla. This effect also reduces vestibular incitation and labyrinth excitability. 

The results of clinical trials demonstrate that meclizine exerts an inhibitory influence on eye movement reflexes related explicitly to low accelerations during visual-vestibular (VIS+VES) tasks. This finding suggests that meclizine's mechanism of action may not primarily involve sensory-specific pathways but rather operates at a more central level. Meclizine addresses motion sickness induced by routine activities; its use may not be effective in vertigo caused by high acceleration.[11]

Pharmacokinetics

Absorption: Meclizine is absorbed post-oral administration. The drug reaches peak plasma levels roughly 3 hours after administration. The onset of action is about 1 hour after oral administration.

Distribution: The results of a pharmacokinetic study revealed that meclizine has a volume of distribution of approximately 6.78 ± 3.52 L.[12] Meclizine can cross the blood-brain barrier.[13]

Metabolism: The data on meclizine metabolism are limited, but according to in vitro metabolic studies, the dominant hepatic enzyme that metabolizes meclizine was found to be CYP2D6.

Elimination: The drug is excreted as a metabolite in the urine and is excreted unchanged in the feces. Meclizine's half-life is about 6 hours, and the duration of action is approximately 8 to 24 hours.[14]

Administration

Available Dosage Forms

Meclizine administration is administered as chewable or non-chewable oral tablets. The dose for oral tablets is 25 to 50 mg. Chewable tablets are available as 25 mg. Chewable tablets must be crushed or completely chewed before swallowing. The drug can be taken without regard to food.

Adult Dosing

Motion sickness: The recommended dosages for controlling motion sickness are 25 to 50 mg orally, taken 1 hour before embarking to protect against motion sickness. Additional doses can be repeated once every 24 hours as necessary.

Vertigo: The recommended daily oral dosages for controlling vertigo in vestibular diseases range from 25 to 100 mg. Subsequent dosages should be adjusted based on the individual's clinical response.[1]

Mèniére disease: The recommended dose of meclizine is 12.5 to 25 mg every 8 hours.[3]

Radiation-induced nausea and vomiting: 50 mg orally 2 to 12 hours before radiotherapy treatment.

Specific Patient Population

Hepatic impairment: There is limited data on how hepatic impairment affects the pharmacokinetics of meclizine. Hepatic impairment could increase systemic exposure to the drug because the liver metabolizes meclizine. Caution is necessary when administering meclizine in patients with hepatic impairment.

Renal impairment: There is limited data on how renal impairment affects the pharmacokinetics of meclizine. Because the drug is renally excreted, there is a potential for the drug/metabolite to accumulate. In such cases, meclizine administration requires caution in patients with reduced renal function.

Pregnancy considerations: Preclinical studies showed meclizine increases the risk of developing cleft palate when given increased doses 25 to 50 times more than the recommended human dose.[15] Meclizine is a former FDA Pregnancy Category B drug. Meclizine is safe to use to treat nausea and vomiting during pregnancy and is not thought to harm an unborn baby.

Breastfeeding considerations: There have not been any documented problems in nursing mothers. Periodic administration of meclizine is likely acceptable while breastfeeding. Extended use and hefty doses of meclizine may cause effects in breastfeeding or decrease the milk supply, especially in combination with sympathomimetic drugs such as pseudoephedrine.[16]

Pediatric patients: The drug is not approved for children younger than 12 because safety and efficacy have not been established. For children 12 and older, dosing is similar to that of adults and adolescents.

Older patients: According to the American Geriatrics Society (AGS Beers Criteria 2023), the long-term use of anticholinergic medications such as meclizine is associated with an elevated risk of delirium, falls, delirium, and dementia among older adults. Evaluate the overall anticholinergic burden when conducting routine annual check-ups.[17] Meclizine may cause urinary retention and amnesia in older adults. Clinicians should prescribe meclizine at the lowest dosage for older patients.

Adverse Effects

Common adverse effects of patients taking meclizine include drowsiness, urinary retention, dry mouth, headache, fatigue, and vomiting.[18] On rare occasions, there have been reports of blurred vision and anaphylactic reactions when taking meclizine.[19]

Drug-Drug Interactions

Due to meclizine's anticholinergic and CNS depressant properties, the drug has the potential to interact with a variety of medications, especially those with anticholinergic and sedative properties. Patients should avoid alcoholic beverages, tranquilizers, and sedatives while taking meclizine due to an increased risk of central nervous system depression.[20]

Due to meclizine's metabolism by CYP2D6, meclizine has the potential for drug interactions with CYP2D6 inhibitors. Consequently, clinicians must closely monitor for adverse reactions and assess the clinical effects when meclizine is co-administered with CYP2D6 inhibitors. Anticholinergic drugs or drugs with anticholinergic properties taken with meclizine may also increase anticholinergic effects.[5]

Contraindications

Meclizine is contraindicated in individuals with a history of hypersensitivity to the drug or excipients like tartrazine. Tartrazine-containing formulations can be associated with allergic reactions.[21]

Warning and Precautions

Drowsiness: Patients should be warned of the possibility of sedation due to meclizine and advised against operating hazardous machinery or driving a car.

Ileus: The anticholinergic effects of meclizine can reduce GI tone and motility. This can aggravate ileus and worsen pyloro-duodenal GI obstruction.

Comorbidities: The potential anticholinergic actions of meclizine pose a risk to patients with asthma, glaucoma, or benign prostatic hyperplasia (BPH). Antihistamines like meclizine can induce acute angle closure glaucoma due to anticholinergic properties.[22] Caution is necessary with the use of the drug in such patients. Patients with bladder obstruction or BPH are at risk for urinary retention due to anticholinergic adverse effects of meclizine.

Genetic polymorphism: The genetic variability in the CYP2D6 enzyme results in different phenotypes, including poor, intermediate, extensive, and ultrarapid metabolizers. These phenotypic variations have a significant impact on the metabolism of meclizine. Prescribers should monitor for potential adverse reactions and evaluate the clinical effectiveness when prescribing meclizine to patients with CYP2D6 polymorphisms.[12]

Phenylketonuria: Some meclizine products contain phenylalanine. Use with caution in patients with phenylketonuria.[23]

Monitoring

Meclizine has not been shown to require serum testing for monitoring. There is no established therapeutic level for meclizine. Just like any drug, patients require clinical monitoring for any adverse reactions.

Due to meclizine's anticholinergic effects, its ability to cause CNS depression, and its metabolism by CYP enzymes, the drug has the potential to interact with a large variety of different medications.[17] Before prescribing, the healthcare provider should carefully review a patient's current medication list and past medical history to avoid interactions, systemic drug accumulation, and exacerbating an already established ailment.

Toxicity

There are no specific antidotes available for meclizine overdose. Treatment is primarily supportive and focused on symptoms. Symptoms of an overdose may include signs of CNS depression such as drowsiness, seizures, and coma. Hypotension can occur, but it is more likely to be seen in older people. The anticholinergic effects and CNS stimulation of an overdose in children can present with hallucinations, seizures, and insomnia.[20] With recent ingestion, induce emesis or perform gastric lavage to prevent further drug absorption. Activated charcoal is also an option. There is no known antidote for meclizine, but physostigmine can help to counter the systemic anticholinergic effects of meclizine.[24]

Enhancing Healthcare Team Outcomes

Meclizine is a commonly prescribed drug by many healthcare professionals, including primary care providers, emergency medicine physicians, oncologists, internists, and advanced practice practitioners. When prescribing this medication, all healthcare practitioners should be aware of the common adverse reactions of the drug and the most susceptible population. The successful use of the drug also depends on the patient's adherence to and knowledge of the potential effects of the drug.

Patients should be aware of the drowsiness and fatigue that the drug can cause so they can avoid driving or operating dangerous machinery when taken. Due to the CNS depression effects of meclizine, healthcare providers should emphasize not drinking alcohol or taking other drugs that can potentiate this effect. Older patients and patients with comorbidities such as asthma, glaucoma, and BPH should be aware of the drug's anticholinergic properties to avoid further complications or be educated on what to do should they arrive.[20]

Other interprofessional healthcare team members, such as pharmacists, should collaborate with prescribers to guarantee that the patient understands proper administration, dosing, and knowledge of potential drug interactions. Clinical nurses should be aware of the adverse effects of the medication and monitor patients. All healthcare professionals must be aware of possible negative outcomes and work together to prevent, manage, and treat accordingly if such an event should occur. Interprofessional collaboration with open communication and shared decision-making will lead to successful outcomes when prescribing meclizine.

References


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Nakashima T, Pyykkö I, Arroll MA, Casselbrant ML, Foster CA, Manzoor NF, Megerian CA, Naganawa S, Young YH. Meniere's disease. Nature reviews. Disease primers. 2016 May 12:2():16028. doi: 10.1038/nrdp.2016.28. Epub 2016 May 12     [PubMed PMID: 27170253]


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Basura GJ, Adams ME, Monfared A, Schwartz SR, Antonelli PJ, Burkard R, Bush ML, Bykowski J, Colandrea M, Derebery J, Kelly EA, Kerber KA, Koopman CF, Kuch AA, Marcolini E, McKinnon BJ, Ruckenstein MJ, Valenzuela CV, Vosooney A, Walsh SA, Nnacheta LC, Dhepyasuwan N, Buchanan EM. Clinical Practice Guideline: Ménière's Disease. Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery. 2020 Apr:162(2_suppl):S1-S55. doi: 10.1177/0194599820909438. Epub     [PubMed PMID: 32267799]

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Wang Z, Lee B, Pearce D, Qian S, Wang Y, Zhang Q, Chow MS. Meclizine metabolism and pharmacokinetics: formulation on its absorption. Journal of clinical pharmacology. 2012 Sep:52(9):1343-9. doi: 10.1177/0091270011414575. Epub 2011 Sep 8     [PubMed PMID: 21903894]

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Gohil VM, Offner N, Walker JA, Sheth SA, Fossale E, Gusella JF, MacDonald ME, Neri C, Mootha VK. Meclizine is neuroprotective in models of Huntington's disease. Human molecular genetics. 2011 Jan 15:20(2):294-300. doi: 10.1093/hmg/ddq464. Epub 2010 Oct 25     [PubMed PMID: 20977989]

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Qazi F, Shoaib MH, Yousuf RI, Nasiri MI, Ahmed K, Ahmad M. Lipids bearing extruded-spheronized pellets for extended release of poorly soluble antiemetic agent-Meclizine HCl. Lipids in health and disease. 2017 Apr 12:16(1):75. doi: 10.1186/s12944-017-0466-x. Epub 2017 Apr 12     [PubMed PMID: 28403892]


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. Meclizine. Drugs and Lactation Database (LactMed®). 2006:():     [PubMed PMID: 30000495]


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Rajan JP, Simon RA, Bosso JV. Prevalence of sensitivity to food and drug additives in patients with chronic idiopathic urticaria. The journal of allergy and clinical immunology. In practice. 2014 Mar-Apr:2(2):168-71. doi: 10.1016/j.jaip.2013.10.002. Epub 2013 Dec 8     [PubMed PMID: 24607044]


[22]

Ah-Kee EY, Egong E, Shafi A, Lim LT, Yim JL. A review of drug-induced acute angle closure glaucoma for non-ophthalmologists. Qatar medical journal. 2015:2015(1):6. doi: 10.5339/qmj.2015.6. Epub 2015 May 10     [PubMed PMID: 26535174]


[23]

van Wegberg AMJ, MacDonald A, Ahring K, Bélanger-Quintana A, Blau N, Bosch AM, Burlina A, Campistol J, Feillet F, Giżewska M, Huijbregts SC, Kearney S, Leuzzi V, Maillot F, Muntau AC, van Rijn M, Trefz F, Walter JH, van Spronsen FJ. The complete European guidelines on phenylketonuria: diagnosis and treatment. Orphanet journal of rare diseases. 2017 Oct 12:12(1):162. doi: 10.1186/s13023-017-0685-2. Epub 2017 Oct 12     [PubMed PMID: 29025426]


[24]

Boley SP, Stellpflug SJ. A Comparison of Resource Utilization in the Management of Anticholinergic Delirium Between Physostigmine and Nonantidote Therapy. The Annals of pharmacotherapy. 2019 Oct:53(10):1026-1032. doi: 10.1177/1060028019846654. Epub 2019 Apr 25     [PubMed PMID: 31023063]