CLINICAL PHARMACOLOGY SECTION

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

The precise mechanism by which meclizine exerts its therapeutic effect is unknown but is presumed to involve antagonism of the histamine H1 receptor.

12.2 Pharmacodynamics

There are no relevant pharmacodynamic data regarding meclizine.

12.3 Pharmacokinetics

The available pharmacokinetic information for meclizine following oral administration has been summarized from published literature.

Absorption
Meclizine is absorbed after oral administration with maximum plasma concentrations reaching at a median Tmax value of 3 hours post-dose (range: 1.5 to 6 hours) for the tablet dosage form.

Distribution
Drug distribution characteristics for meclizine in humans are unknown.

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

Metabolism
In an in vitro metabolic study using human hepatic microsome and recombinant CYP enzyme, CYP2D6 was found to be the dominant enzyme for metabolism of meclizine.

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DRUG INTERACTIONS SECTION

Highlight: * Coadministration of meclizine hydrochloride with other CNS depressants, including alcohol, may result in increased CNS depression (7.1).

• CYP2D6 inhibitors: As meclizine is metabolized by CYP2D6, there is a potential for drug-drug interactions between meclizine hydrochloride and CYP2D6 inhibitors (7.2).

7 DRUG INTERACTIONS

7.1 CNS Depressants

There may be increased CNS depression when meclizine hydrochloride is administered concurrently with other CNS depressants, including alcohol [see Warnings and Precautions (5.1)].

7.2 CYP2D6 Inhibitors

Based on in-vitro evaluation, meclizine is metabolized by CYP2D6. Therefore, there is a possibility for a drug interaction between meclizine hydrochloride and CYP2D6 inhibitors. Therefore, monitor for adverse reactions and clinical effect accordingly.

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USE IN SPECIFIC POPULATIONS SECTION

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Risk Summary
Data from epidemiological studies have not generally indicated a drug- associated risk of major birth defects with meclizine during pregnancy. However, in a published study, an increased incidence of fetal malformations was observed following oral administration of meclizine to pregnant rats during the period of organogenesis, at doses similar to those used clinically.

In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown.

Data
Human Data
Epidemiological studies reporting on pregnancies exposed to meclizine have not identified an association between the use of meclizine during pregnancy and an increased risk of major birth defects.

Animal Data
In a published study, oral administration of meclizine (25-250 mg/kg) to pregnant rats during the period of organogenesis resulted in a high incidence of fetal malformations. These effects occurred at doses as low as
25 mg/kg, which is approximately 2 times the maximum recommended human dose (100 mg) on a body surface area (mg/m2) basis.

8.2 Lactation

Risk Summary
There are no data on the presence of meclizine in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for meclizine hydrochloride and any potential adverse effects on the breastfed infant from meclizine hydrochloride or from the underlying maternal condition.

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established.

8.5 Geriatric Use

In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

8.6 Hepatic Impairment

The effect of hepatic impairment on the pharmacokinetics of meclizine has not been evaluated. As meclizine hydrochloride undergoes metabolism, hepatic impairment may result in increased systemic exposure of meclizine. Treatment with meclizine hydrochloride should be administered with caution in patients with hepatic impairment.

8.7 Renal Impairment

The effect of renal impairment on the pharmacokinetics of meclizine has not been evaluated. Because of a potential for drug/metabolite accumulation, meclizine hydrochloride should be administered with caution in patients with renal impairment and in the elderly, as renal function generally declines with age.

8.8 Genetic CYP2D6 Polymorphism

The genetic polymorphism of CYP2D6 that results in poor-, intermediate-, extensive-, and ultrarapid metabolizer phenotypes could contribute to large inter-individual variability in meclizine exposure. Therefore, when meclizine hydrochloride is administered to patients with CYP2D6 polymorphism, monitor for adverse reactions and clinical effect accordingly.

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NONCLINICAL TOXICOLOGY SECTION

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis
Animal studies to assess the carcinogenic potential of meclizine have not been conducted.

Mutagenesis
Genetic toxicology studies of meclizine have not been conducted.

Impairment of Fertility
Animal studies to assess the effects of meclizine on fertility and early embryonic development have not been conducted.

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INFORMATION FOR PATIENTS SECTION

17 PATIENT COUNSELING INFORMATION

Administration Instructions
Advise patients that the tablets must be swallowed whole, but chewable tablets must be chewed or crushed completely before swallowing [see Dosage and Administration (2.1)].

Adverse Reactions
Advise patients that meclizine hydrochloride may cause anaphylactic reaction, drowsiness, dry mouth, headache, fatigue, vomiting and, on rare occasions, blurred vision [see Warnings and Precautions (5.1), Adverse Reactions (6)].
Inform patients that meclizine hydrochloride may impair their ability to engage in potentially dangerous activities, such as operating machinery or vehicles.

Concomitant Drug Interactions
Advise patients regarding medications that should not be taken in combination with meclizine hydrochloride or that may necessitate increased monitoring [see Drug Interactions (7.1, 7.2)]. Inform patients that alcohol may increase adverse reactions.

Concurrent Medical Conditions
Advise patients to notify their healthcare provider about all of their medical conditions, including if they are pregnant or plan to become pregnant or if they are breastfeeding [see Warnings and Precautions (5.2), Use in Specific Populations (8.1, 8.2)].

PIA66201-00

Distributed by:
Rising Pharmaceuticals, Inc.
Saddle Brook, NJ 07663

Issued: 08/2019

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