Clemastine (Monograph)

Brand names: Dayhist, Tavist
Drug class: First Generation Antihistamines

Medically reviewed by Drugs.com on Jan 22, 2025. Written by ASHP.

Introduction

First generation antihistamine; an ethanolamine derivative.

Uses for Clemastine

Allergic Rhinitis

Symptomatic relief of rhinorrhea, sneezing, lacrimation, itching eyes, or oronasopharyngeal itching associated with allergic rhinitis (e.g., hay fever) or other upper respiratory allergies.

Allergic Skin Disorders

Management of mild, uncomplicated allergic skin manifestations of urticaria and angioedema.

Common Cold

Self-medication for temporary relief of symptoms associated with the common cold (e.g., rhinorrhea, sneezing).

Clemastine Dosage and Administration

Administration

Oral Administration

Administer orally as tablets or oral solution.

Dosage

Available as clemastine fumarate; dosage expressed in terms of the salt.

1.34 mg clemastine fumarate equivalent to 1 mg clemastine.

Individualize dosage according to patient’s response and tolerance.

Pediatric Patients

Allergic Conditions

Allergic Rhinitis

Oral

Children 6 to <12 years of age: Initially, 0.67 mg twice daily (as oral solution). Because single doses of up to 3.02 mg have been well tolerated, may increase dosage as necessary, not to exceed 4.02 mg daily.

Children ≥12 years of age: 1.34 mg every 12 hours (as tablets or oral solution); this is the maximum dosage recommended for self-medication. When used under the direction of a clinician, may increase dosage as necessary, not to exceed 8.04 mg daily.

Allergic Skin Disorders

Oral

Children 6 to <12 years of age: Initially, 1.34 mg twice daily (as oral solution). May increase dosage as necessary, not to exceed 4.02 mg daily.

Children ≥12 years of age: 2.68 mg 1–3 times daily (as tablets or oral solution), not to exceed 8.04 mg daily.

Common Cold

Oral

Self-medication in children ≥12 years of age: Usually, 1.34 mg every 12 hours (as tablets), not to exceed 2.68 mg daily unless otherwise directed by a clinician.

Adults

Allergic Conditions

Allergic Rhinitis

Oral

Initially, 1.34 mg every 12 hours (as tablets or oral solution); this is the maximum dosage recommended for self-medication. When used under the direction of a clinician, may increase dosage as necessary, not to exceed 8.04 mg daily.

Allergic Skin Disorders

Oral

2.68 mg 1–3 times daily (as tablets or oral solution), not to exceed 8.04 mg daily.

Common Cold

Oral

Self-medication: Usually, 1.34 mg every 12 hours (as tablets), not to exceed 2.68 mg daily unless otherwise directed by a clinician.

Prescribing Limits

Pediatric Patients

Allergic Conditions

Allergic Rhinitis

Oral

Children 6 to <12 years of age: Maximum 4.02 mg daily.

Children ≥12 years of age: For self-medication, maximum 1.34 mg every 12 hours. When used under the direction of a clinician, maximum 8.04 mg daily.

Allergic Skin Disorders

Oral

Children 6 to <12 years of age: Maximum 4.02 mg daily.

Children ≥12 years of age: Maximum 8.04 mg daily.

Common Cold

Oral

Children ≥12 years of age: For self-medication, maximum 2.68 mg daily unless otherwise directed by a clinician.

Adults

Allergic Conditions

Allergic Rhinitis

Oral

Self-medication: Maximum 1.34 mg every 12 hours. When used under the direction of a clinician, maximum 8.04 mg daily.

Allergic Skin Disorders

Oral

Maximum 8.04 mg daily.

Common Cold

Oral

Self-medication: Maximum 2.68 mg daily unless otherwise directed by a clinician.

Special Populations

Geriatric Patients

Reduce dosage if mild adverse effects occur. (See Geriatric Use under Cautions.)

Cautions for Clemastine

Contraindications

• Use contraindicated in neonates and premature infants. (See Pediatric Use under Cautions.)

• Women who are breast-feeding. (See Lactation under Cautions.)

• Patients receiving MAO inhibitor therapy. (See Interactions.)

• Known hypersensitivity to clemastine, other antihistamines with similar chemical structure, or any ingredient in the formulation.

Warnings/Precautions

Warnings

Concomitant Diseases

Because of anticholinergic effects, use with extreme caution in patients with angle-closure glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, bladder neck obstruction, or symptomatic prostatic hypertrophy.

Use with caution in patients with history of bronchial asthma, increased IOP, hyperthyroidism, or cardiovascular disease (e.g., hypertension).

CNS Effects

Risk of drowsiness. (See CNS Depressants under Interactions and also see Advice to Patients.)

Possible excitability (especially in children). (See Pediatric Use under Cautions.)

Specific Populations

Pregnancy

Category B.

Lactation

Distributed into milk. Some manufacturers recommend discontinuance of nursing or the drug because of potential risk to nursing infants (see Contraindications under Cautions). However, AAP states that the drug may be used with caution during breast-feeding.

Pediatric Use

Contraindicated in neonates and premature infants.

Possible paradoxical excitement (e.g., restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures), especially in children.

Safety and efficacy of tablets not established in children <12 years of age. Safety and efficacy of oral solution not established in children <6 years of age.

Risk of overdosage and toxicity (including death) in children <2 years of age receiving OTC preparations containing antihistamines, cough suppressants, expectorants, and nasal decongestants alone or in combination for relief of symptoms of upper respiratory tract infection. Limited evidence of efficacy for these preparations in this age group; appropriate dosages not established. Therefore, FDA recommended not to use such preparations in children <2 years of age; safety and efficacy in older children under evaluation. Because children 2–3 years of age also are at increased risk of overdosage and toxicity, some manufacturers of oral nonprescription cough and cold preparations agreed to voluntarily revise the product labeling to state that such preparations should not be used in children <4 years of age. FDA recommends that parents and caregivers adhere to dosage instructions and warnings on the product labeling that accompanies the preparation and consult a clinician about any concerns. Clinicians should ask caregivers about use of OTC cough/cold preparations to avoid overdosage.

Geriatric Use

Possible increased risk of dizziness, sedation, and hypotension in patients ≥60 years of age. (See Geriatric Patients under Dosage and Administration.)

Common Adverse Effects

Sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, thickening of bronchial secretions.

Drug Interactions

Specific Drugs and Laboratory Tests

Clemastine Pharmacokinetics

Absorption

Bioavailability

Rapidly and almost completely absorbed from the GI tract.

Peak plasma concentrations achieved within 2–5 hours following oral administration.

Onset

Antihistaminic effect is maximal within 5–7 hours.

Duration

Antihistaminic effect persists for 10–12 hours and, in some individuals, up to 24 hours.

Distribution

Extent

Distribution into human body fluids and tissues not fully characterized.

Distributed into milk.

Elimination

Metabolism

Exact metabolic fate not clearly established, but appears to be extensively metabolized.

Elimination Route

Excreted principally in urine as unchanged drug and metabolites.

Stability

Storage

Oral

Tablets

Tight, light-resistant containers at 20–25°C.

Oral Solution

Tight, light-resistant, upright containers at 20–25°C.

Actions

• Blocks H₁-receptor sites, thereby preventing the action of histamine on the cell.

• Suppresses flare and pruritus that accompany the endogenous release of histamine.

• Has anticholinergic and sedative effects.

• Antihistamines do not block the stimulating effect of histamine on gastric acid secretion, which is mediated by H₂-receptors of the parietal cells.

Advice to Patients

• Risk of drowsiness; avoid alcohol and avoid engaging in hazardous tasks (e.g., operating machinery, driving a motor vehicle) until effects on individual are known.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and dietary or herbal supplements, as well as any concomitant illnesses. Importance of patients already receiving another CNS depressant (e.g., sedative, tranquilizer) not undertaking self-medication without first consulting a clinician.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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