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Pronunciation
(KLEM as teen)
U.S. Brand Names
Index Terms
Generic Available
Yes
Pharmacologic Category
Pharmacologic Category Synonyms
Use: Labeled Indications
Perennial and seasonal allergic rhinitis and other allergic symptoms including urticaria
Pregnancy Risk Factor
B
Lactation
Enters breast milk/not recommended
Contraindications
Hypersensitivity to clemastine or any component of the formulation; narrow-angle glaucoma
Warnings/Precautions
Concerns related to adverse effects:
• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks which require mental alertness (eg, operating machinery or driving).
Disease-related concerns:
• Asthma: Use with caution in patients with a history of asthma.
• Cardiovascular disease: Use with caution in patients with cardiovascular disease (including hypertension and ischemic heart disease).
• Increased intraocular pressure: Use with caution in patients with increased intraocular pressure.
• Prostatic hyperplasia/urinary obstruction: Use with caution in patients with prostatic hyperplasia and/or GU obstruction.
• Pyloroduodenal obstruction: Use with caution in patients with pyloroduodenal obstruction (including stenotic peptic ulcer).
• Thyroid dysfunction: Use with caution in patients with thyroid dysfunction.
Concurrent drug therapy issues:
• Sedatives: Effects may be potentiated when used with other sedative drugs or ethanol.
Special populations:
• Elderly: Use with caution in the elderly; may be more sensitive to adverse effects.
• Pediatrics: Safety and efficacy have not been established in children <6 years of age.
Adverse Reactions
Frequency not defined.
Cardiovascular: Palpitation, hypotension, tachycardia
Central nervous system: Dyscoordination, sedation, somnolence slight to moderate, sleepiness, confusion, restlessness, nervousness, insomnia, irritability, fatigue, headache, dizziness increased
Dermatologic: Rash, photosensitivity
Gastrointestinal: Diarrhea, nausea, xerostomia, epigastric distress, vomiting, constipation
Genitourinary: Urinary frequency, difficult urination, urinary retention
Hematologic: Hemolytic anemia, thrombocytopenia, agranulocytosis
Ocular: Blurred vision
Otic: Tinnitus
Respiratory: Thickening of bronchial secretions
Miscellaneous: Anaphylaxis
Metabolism/Transport Effects
Inhibits CYP2D6 (weak), 3A4 (weak)
Drug Interactions
Acetylcholinesterase Inhibitors (Central): Anticholinergics may diminish the therapeutic effect of Acetylcholinesterase Inhibitors (Central). Acetylcholinesterase Inhibitors (Central) may diminish the therapeutic effect of Anticholinergics. If the anticholinergic action is a side effect of the agent, the result may be beneficial. Risk C: Monitor therapy
Alcohol (Ethyl): CNS Depressants may enhance the CNS depressant effect of Alcohol (Ethyl). Risk C: Monitor therapy
Amphetamines: May diminish the sedative effect of Antihistamines. Risk C: Monitor therapy
Anticholinergics: May enhance the adverse/toxic effect of other Anticholinergics. Exceptions: Paliperidone. Risk C: Monitor therapy
Betahistine: Antihistamines may diminish the therapeutic effect of Betahistine. Risk C: Monitor therapy
CNS Depressants: May enhance the adverse/toxic effect of other CNS Depressants. Risk C: Monitor therapy
Pramlintide: May enhance the anticholinergic effect of Anticholinergics. These effects are specific to the GI tract. Risk D: Consider therapy modification
Ethanol/Nutrition/Herb Interactions
Ethanol: Avoid ethanol (may increase CNS depression).
Mechanism of Action
Competes with histamine for H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract
Pharmacodynamics/Kinetics
Onset of action: Peak effect: Therapeutic: 5-7 hours
Duration: 8-16 hours
Absorption: Almost complete
Metabolism: Hepatic
Excretion: Urine
Dosage
Oral:
Infants and Children <6 years: 0.05 mg/kg/day as clemastine base or 0.335-0.67 mg/day clemastine fumarate (0.25-0.5 mg base/day) divided into 2 or 3 doses; maximum daily dosage: 1.34 mg (1 mg base)
Children 6-12 years: 0.67-1.34 mg clemastine fumarate (0.5-1 mg base) twice daily; do not exceed 4.02 mg/day (3 mg/day base)
Children ?12 years and Adults:
1.34 mg clemastine fumarate (1 mg base) twice daily to 2.68 mg (2 mg base) 3 times/day; do not exceed 8.04 mg/day (6 mg base)
OTC labeling: 1.34 mg clemastine fumarate (1 mg base) twice daily; do not exceed 2 mg base/24 hours
Elderly: Lower doses should be considered in patients >60 years
Monitoring Parameters
Look for a reduction of rhinitis, urticaria, eczema, pruritus, or other allergic symptoms
Dental Health: Effects on Dental Treatment
Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation).
Dental Health: Vasoconstrictor/Local Anesthetic Precautions
No information available to require special precautions
Mental Health: Effects on Mental Status
Drowsiness is common; may cause nervousness; rare reports of depression
Mental Health: Effects on Psychiatric Treatment
Concurrent use with psychotropics may result in additive sedation
Dosage Forms
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Syrup, as fumarate: 0.67 mg/5 mL (120 mL, 480 mL) [prescription formulation; 0.5 mg base/5 mL]
Tablet, as fumarate: 1.34 mg [1 mg base; OTC], 2.68 mg [2 mg base; prescription formulation]
Dayhist® Allergy [DSC], Tavist® Allergy: 1.34 mg [1 mg base]
Pricing: U.S. (www.drugstore.com)
Syrup (Clemastine Fumarate)
0.67 mg/5 mL (120): $18.98
Tablets (Clemastine Fumarate)
1.34 mg (100): $25.99
2.68 mg (30): $17.99
References
American Academy of Pediatrics Committee on Drugs, “The Transfer of Drugs and Other Chemicals Into Human Milk,” Pediatrics, 2001, 108(3):776-89.
Kok TH, Taitz LS, Bennett MJ, et al, “Drowsiness Due to Clemastine Transmitted in Breast Milk,” Lancet, 1982, 1:914-5.
International Brand Names
Lexi-Comp.com
Last full review/revision November 2009
Content last modified November 2009
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