Clemastine (Monograph)

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

Medically reviewed by Drugs.com on Jan 22, 2024. Written by ASHP.

Introduction

First generation antihistamine; an ethanolamine derivative.^{101 102 103 a b}

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.^{101 102 103 104 105 a}

Allergic Skin Disorders

Management of mild, uncomplicated allergic skin manifestations of urticaria and angioedema.^{101 102 103 a}

Common Cold

Self-medication for temporary relief of symptoms associated with the common cold (e.g., rhinorrhea, sneezing).^{105 a}

Clemastine Dosage and Administration

Administration

Oral Administration

Administer orally as tablets or oral solution.^{101 102 103 a}

Dosage

Available as clemastine fumarate; dosage expressed in terms of the salt.^{101 102 103 104}

1.34 mg clemastine fumarate equivalent to 1 mg clemastine.^{101 103 104 105 a}

Individualize dosage according to patient’s response and tolerance.^{101 102 103 a b}

Pediatric Patients

Allergic Conditions

Allergic Rhinitis

Oral

Children 6 to <12 years of age: Initially, 0.67 mg twice daily (as oral solution).^{101 103 a} 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.^{101 103 a}

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.^{104 105 a} When used under the direction of a clinician, may increase dosage as necessary, not to exceed 8.04 mg daily.^{101 102 103 a}

Allergic Skin Disorders

Oral

Children 6 to <12 years of age: Initially, 1.34 mg twice daily (as oral solution).¹⁰¹ May increase dosage as necessary, not to exceed 4.02 mg daily.^{101 103 a}

Children ≥12 years of age: 2.68 mg 1–3 times daily (as tablets or oral solution), not to exceed 8.04 mg daily.^{101 102 103 a}

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.^a

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.^a When used under the direction of a clinician, may increase dosage as necessary, not to exceed 8.04 mg daily.^{101 102 103 a}

Allergic Skin Disorders

Oral

2.68 mg 1–3 times daily (as tablets or oral solution), not to exceed 8.04 mg daily.^{101 102 103 a}

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.^a

Prescribing Limits

Pediatric Patients

Allergic Conditions

Allergic Rhinitis

Oral

Children 6 to <12 years of age: Maximum 4.02 mg daily.^{101 a}

Children ≥12 years of age: For self-medication, maximum 1.34 mg every 12 hours.^a When used under the direction of a clinician, maximum 8.04 mg daily.^{101 102 a}

Allergic Skin Disorders

Oral

Children 6 to <12 years of age: Maximum 4.02 mg daily.^{101 a}

Children ≥12 years of age: Maximum 8.04 mg daily.^{101 102 a}

Common Cold

Oral

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

Adults

Allergic Conditions

Allergic Rhinitis

Oral

Self-medication: Maximum 1.34 mg every 12 hours.^a When used under the direction of a clinician, maximum 8.04 mg daily.^{101 102 a}

Allergic Skin Disorders

Oral

Maximum 8.04 mg daily.^{101 102 a}

Common Cold

Oral

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

Special Populations

Geriatric Patients

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

Cautions for Clemastine

Contraindications

• Use contraindicated in neonates and premature infants.^{101 103 a} (See Pediatric Use under Cautions.)

• Women who are breast-feeding.^{101 102 103} (See Lactation under Cautions.)

• Patients receiving MAO inhibitor therapy.¹⁰² (See Interactions.)

• Known hypersensitivity to clemastine, other antihistamines with similar chemical structure, or any ingredient in the formulation.^{101 102 103}

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.^{101 102 103 b}

Use with caution in patients with history of bronchial asthma, increased IOP, hyperthyroidism, or cardiovascular disease (e.g., hypertension).^{101 102 103}

CNS Effects

Risk of drowsiness.^{101 103 b} (See CNS Depressants under Interactions and also see Advice to Patients.)

Possible excitability (especially in children).^{104 105 b} (See Pediatric Use under Cautions.)

Specific Populations

Pregnancy

Category B.^{101 103 106}

Lactation

Distributed into milk.^c Some manufacturers recommend discontinuance of nursing or the drug because of potential risk to nursing infants (see Contraindications under Cautions).^{101 102 103 s} However, AAP states that the drug may be used with caution during breast-feeding.¹⁰⁶

Pediatric Use

Contraindicated in neonates and premature infants.^{101 103 a}

Possible paradoxical excitement (e.g., restlessness, insomnia, tremors, euphoria, nervousness, delirium, palpitation, seizures), especially in children.^{104 105 b}

Safety and efficacy of tablets not established in children <12 years of age.^{102 a} Safety and efficacy of oral solution not established in children <6 years of age.^{101 103 a}

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.^{d v} Limited evidence of efficacy for these preparations in this age group; appropriate dosages not established.^d Therefore, FDA recommended not to use such preparations in children <2 years of age;^e safety and efficacy in older children under evaluation.^{g i} 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.^{f g h i} 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.^{f g h} Clinicians should ask caregivers about use of OTC cough/cold preparations to avoid overdosage.^d

Geriatric Use

Possible increased risk of dizziness, sedation, and hypotension in patients ≥60 years of age.^{101 102 103} (See Geriatric Patients under Dosage and Administration.)

Common Adverse Effects

Sedation,^{101 102 103} sleepiness,^{101 102 103} dizziness,^{101 102 103} disturbed coordination,^{101 102 103} epigastric distress,^{101 102 103} thickening of bronchial secretions.^{101 102 103}

Drug Interactions

Specific Drugs and Laboratory Tests

Clemastine Pharmacokinetics

Absorption

Bioavailability

Rapidly and almost completely absorbed from the GI tract.^{101 102 103 a}

Peak plasma concentrations achieved within 2–5 hours following oral administration.^{101 102 103 s t u}

Onset

Antihistaminic effect is maximal within 5–7 hours.^{101 102 103 s}

Duration

Antihistaminic effect persists for 10–12 hours and, in some individuals, up to 24 hours.^{101 102 103 s}

Distribution

Extent

Distribution into human body fluids and tissues not fully characterized.^{c s}

Distributed into milk.^c

Elimination

Metabolism

Exact metabolic fate not clearly established, but appears to be extensively metabolized.^{s t u}

Elimination Route

Excreted principally in urine as unchanged drug and metabolites.^{101 102 103 s t}

Stability

Storage

Oral

Tablets

Tight, light-resistant containers at 20–25°C.¹⁰²

Oral Solution

Tight, light-resistant, upright containers¹⁰³ at 20–25°C.^{101 103}

Actions

• Blocks H₁-receptor sites, thereby preventing the action of histamine on the cell.^{101 103 b}

• Suppresses flare and pruritus that accompany the endogenous release of histamine.^{101 b}

• Has anticholinergic and sedative effects.^{101 102 103}

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

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.^{101 102 103 104 105}

• 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.^{101 102 103} Importance of patients already receiving another CNS depressant (e.g., sedative, tranquilizer) not undertaking self-medication without first consulting a clinician.¹⁰⁴

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.^{101 102 103}

• Importance of informing patients of other important precautionary information.^{101 102 103} (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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