Clemastine Fumarate

Pronunciation: (KLEM-ass-teen FEW-muh-rate)Class: Ethanolamine, nonselective

Trade Names:Dayhist-1- Tablets 1.34 mg as fumarate (equiv. to 1 mg clemastine)

Trade Names:Tavist Allergy- Tablets 1.34 mg as fumarate (equiv. to 1 mg clemastine)

Trade Names:Clemastine Fumarate- Tablets 2.68 mg (equiv. to 2 mg clemastine)- Syrup 0.67 mg per 5 mL (equiv. to 0.5 mg clemastine)


Competitively antagonizes histamine at H 1 receptor sites.



Well absorbed. T max is 2 to 5 h.


Excreted in breast milk.


Metabolized in the liver by mono- and didemethylation and glucuronide conjugation.


Excreted mainly via urine.


5 to 7 h.


10 to 12 h, possibly up to 24 h.

Indications and Usage

Relief of symptoms associated with allergic rhinitis or other upper respiratory allergies, such as sneezing, rhinorrhea, pruritus, and lacrimation; relief of mild, uncomplicated allergic skin manifestation of urticaria and angioedema.


Hypersensitivity to antihistamines; MAOI therapy; use in newborn or premature infants and in nursing women.

Dosage and Administration

TabletsAdults and Children 12 yr of age and older

PO 1.34 mg every 12 h (max 2.68 mg every 24 h).

Children younger than 12 yr of age

Consult a doctor.

SyrupAdults and children 12 years of age and older

PO 1.34 mg bid.

Children 6 to 12 yr of age

PO 0.67 to 1.34 mg bid.

General Advice

  • Administer without regard to meals. Administer with food if GI upset occurs.
  • Measure and administer prescribed dose of oral syrup using dosing syringe, dosing spoon, or dosing cup.


Store 1.34 mg tablets at controlled room temperature (59° to 86°F). Store 2.68 mg tablets and oral syrup below 77°F.

Drug Interactions

Alcohol, CNS depressants

May cause additive CNS depressant effects.


May increase anticholinergic effects of clemastine fumarate.

Laboratory Test Interactions

Skin testing procedures

Drug may prevent or diminish otherwise positive reaction to dermal reactivity indicators.

Adverse Reactions


Orthostatic hypotension; palpitations; bradycardia; tachycardia; arrhythmias.


Acute labyrinthitis; confusion; convulsions; disturbed coordination; dizziness; euphoria; excitation; fatigue; hysteria; insomnia; irritability; nervousness; neuritis; paresthesias; restlessness; sedation; sleepiness; tremor; vertigo.


Blurred vision; tinnitus; diplopia.


Epigastric distress; nausea; vomiting; diarrhea; constipation.


Urinary frequency; difficult urination; urinary retention; early menses.


Hemolytic anemia; thrombocytopenia; agranulocytosis.


Increased appetite; weight gain.


Thickening of bronchial secretions; chest tightness; wheezing; nasal stuffiness; dry mouth, nose and throat; sore throat; respiratory depression.


Hypersensitivity reactions; photosensitivity.



Allergy symptoms

Assess allergy symptoms (eg, cough, rhinitis, nasal congestion, sneezing, watery eyes, itching nose, throat, or eyes) before starting therapy and periodically during therapy. Notify health care provider if symptoms are not improving or are getting worse.


Monitor patient for dizziness and excessive drowsiness. If noted, hold therapy and notify health care provider.

Review therapy

Ensure that therapy is periodically reviewed to determine if therapy needs to be continued without change or if a dose change (eg, increase, decrease, discontinuation) is indicated.




Contraindicated in nursing mothers.



Safety and efficacy not established in children under 12 yr of age.


Safety and efficacy not established in children under 6 yr of age.


Elderly and debilitated patients are at an increased risk of dizziness, excessive sedation, syncope, toxic confusional states, and hypotension. Dosage reduction may be required.

Special Risk Patients

Use drug with caution in patients predisposed to urinary retention, history of bronchial asthma, increased IOP, hyperthyroidism, CV disease, or hypertension. Avoid use in patients with history of sleep apnea. Use with considerable caution in patients with narrow-angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, or bladder neck obstruction.



CNS depression or stimulation, hallucinations, convulsions, CV collapse, dry mouth, fixed dilated pupils, flushing.

Patient Information

  • Advise patient to take each dose without regard to meals but to take with food if stomach upset occurs.
  • Advise patient using tablets to take prescribed every 12 h as ordered.
  • Advise patient or caregiver using oral liquid to administer prescribed every 12 h. Advise patient or caregiver to measure and administer prescribed dose using dosing syringe, dosing spoon, or dosing cup.
  • Advise patient that if a dose is missed to take it as soon as possible unless it is nearing time for the next scheduled dose, then advise patient to skip the missed dose and take the next dose at the regularly scheduled time. Caution patient not to double the dose to catch up.
  • Advise patient that if allergy symptoms are not controlled not to increase the dose of medication or frequency of use but to inform health care provider. Caution patient that larger doses or more frequent dosing does not increase effectiveness and may cause excessive drowsiness or other side effects.
  • Instruct patient to stop taking drug and immediately report any of these symptoms to health care provider: persistent dizziness; excessive drowsiness; severe dry mouth, nose, or throat; flushing; unexplained shortness of breath or difficulty breathing; unusual tiredness or weakness; sore throat, fever, or other signs of infection; bleeding or unusual bruising; fast or irregular heartbeat; excitability, confusion, or changes in thinking or behavior; chest tightness; difficulty urinating.
  • Advise patient that medication may cause drowsiness or dizziness and not to drive or perform other activities requiring mental alertness until tolerance is determined.
  • Advise patient to take sips of water, suck on ice chips or sugarless hard candy, or chew sugarless gum if dry mouth occurs.
  • Caution patient that alcohol and other CNS depressants (eg, sedatives) will have additional sedative effects if taken with clemastine.
  • Caution patient not to take any OTC antihistamines while taking this medication unless advised by health care provider.
  • Caution patient that medication may cause sensitivity to sunlight and to avoid excessive exposure to the sun or UV light (eg, tanning booths) and to wear protective clothing and use sunscreens until tolerance is determined.
  • If patient is to have allergy skin testing, advise patient not to take the medication for at least 4 days before the skin testing.

Copyright © 2009 Wolters Kluwer Health.

  • Clemastine Prescribing Information (FDA)
  • Allerhist-1 MedFacts Consumer Leaflet (Wolters Kluwer)
  • Tavist Consumer Overview