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Pronunciation
(KLEM as teen)
Generic Available (U.S.)
Yes
Index Terms
U.S. Brand Names
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.
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: Levocabastine (Nasal); Paliperidone. Risk C: Monitor therapy
Benzylpenicilloyl Polylysine: Antihistamines may diminish the diagnostic effect of Benzylpenicilloyl Polylysine. Management: Suspend systemic H1 antagonists for benzylpenicilloyl-polylysine skin testing and delay testing until systemic antihistaminic effects have dissipated. A histamine skin test may be used to assess persistent antihistaminic effects. Risk D: Consider therapy modification
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. Exceptions: Levocabastine (Nasal). Risk C: Monitor therapy
Droperidol: May enhance the CNS depressant effect of CNS Depressants. Management: Consider dose reductions of droperidol or of other CNS agents (e.g., opioids, barbiturates) with concomitant use. Risk D: Consider therapy modification
HydrOXYzine: May enhance the CNS depressant effect of CNS Depressants. Management: For patients being treated with hydroxyzine, a reduction in the dose of any other CNS depressants that are to be used in combination is recommended. With concurrent use, monitor patients closely for excessive response to the combination. Risk D: Consider therapy modification
Pramlintide: May enhance the anticholinergic effect of Anticholinergics. These effects are specific to the GI tract. Risk D: Consider therapy modification
Selective Serotonin Reuptake Inhibitors: CNS Depressants may enhance the adverse/toxic effect of Selective Serotonin Reuptake Inhibitors. Specifically, the risk of psychomotor impairment may be enhanced. Risk C: Monitor therapy
Ethanol/Nutrition/Herb Interactions
Ethanol: May increase CNS depression; monitor for increased effects with coadministration. Caution patients about effects.
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.
Syrup, oral, as fumarate: 0.67 mg/5 mL (120 mL) [equivalent to clemastine base 0.5 mg/5 mL; prescription formulation]
Tablet, oral, as fumarate: 1.34 mg [equivalent to clemastine base 1 mg; OTC], 2.68 mg [equivalent to clemastine base 2 mg; prescription formulation]
Tavist® Allergy: 1.34 mg [scored; equivalent to clemastine base 1 mg]
Pricing: U.S. (www.drugstore.com)
Syrup (Clemastine Fumarate)
0.67 mg/5 mL (120): $18.99
Tablets (Clemastine Fumarate)
1.34 mg (100): $25.99
2.68 mg (30): $17.98
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 May 2011
Content last modified May 2011
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