WARNINGS
Antihistamines should be used with considerable caution in patients with: narrow angle glaucoma, stenosing peptic ulcer, pyloroduodenal obstruction, symptomatic prostatic hypertrophy, and bladder neck obstruction.
Use with CNS Depressants
Clemastine has additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.).
Use in Activities Requiring Mental Alertness
Patients should be warned about engaging in activities requiring mental alertness such as driving a car or operating appliances, machinery, etc.
Use in the Elderly (approximately 60 years or older)
Antihistamines are more likely to cause dizziness, sedation, and hypotension in elderly patients.
PRECAUTIONS
General
Clemastine fumarate should be used with caution in patients with: history of bronchial asthma, increased intraocular pressure, hyperthyroidism, cardiovascular disease, and hypertension.
Information for Patients
Patients taking antihistamines should receive the following information and instructions:
- Antihistamines are prescribed to reduce allergic symptoms.
- Patients should be questioned regarding a history of glaucoma, peptic ulcer, urinary retention, or pregnancy before starting antihistamine therapy.
- Patients should be told not to take alcohol, sleeping pills, sedatives, or tranquilizers while taking antihistamines.
- Antihistamines may cause drowsiness, dizziness, dry mouth, blurred vision, weakness, nausea, headache, or nervousness in some patients.
- Patients should avoid driving a car or working with hazardous machinery until they assess the effects of this medicine.
- Patients should be told to store this medicine in a tightly closed container in a dry, cool place away from heat or direct sunlight and out of the reach of children.
Drug Interactions
Additive CNS depression may occur when antihistamines are administered concomitantly with other CNS depressants including barbiturates, tranquilizers, and alcohol. Patients receiving antihistamines should be advised against the concurrent use of other CNS depressant drugs.
Monoamine oxidase (MAO) inhibitors prolong and intensify the anticholinergic effects of antihistamines.
Carcinogenesis, Mutagenesis, Impairment of Fertility
Carcinogenesis and Mutagenesis
In a 2-year oral study in the rat at a dose of 84 mg/kg (about 500 times the adult human dose) and an 85-week oral study in the mouse at 206 mg/kg (about 1300 times the adult human dose), clemastine fumarate showed no evidence of carcinogenesis. No mutagenic studies have been conducted with clemastine fumarate.
Impairment of Fertility
Oral doses of clemastine fumarate in the rat produced a decrease in mating ability of the male at 312 times the adult human dose. This effect was not found at 156 times the adult human dose.
Pregnancy
Teratogenic Effects
Pregnancy category B
Oral reproduction studies performed with clemastine fumarate in rats and rabbits at doses up to 312 and 188 times the adult human doses respectively, have revealed no evidence of teratogenic effects.
There are no adequate and well-controlled studies of clemastine fumarate in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used in pregnancy only if clearly needed.
Nursing Mothers
Although quantitative determinations of antihistaminic drugs in breast milk have not been reported, qualitative tests have documented the excretion of diphenhydramine, pyrilamine, and tripelennamine in human milk.
Because of the potential for adverse reactions in nursing infants from antihistamines, a decision should be made whether to discontinue nursing or to discontinue the drug.
Pediatric Use
The safety and efficacy of Clemastine Fumarate Syrup has been confirmed in the pediatric population (age 6 years through 12). Safety and dose tolerance studies have confirmed pediatric patients 6 through 11 years tolerated dosage ranges of 0.75 to 2.25 mg clemastine. In pediatric patients particularly, antihistamines in overdosage may produce hallucinations, convulsions and death. Symptoms of antihistamine toxicity in pediatric patients may include fixed dilated pupils, flushed face, dry mouth, fever, excitation, hallucinations, ataxia, incoordination, athetosis, tonic-clonic convulsions, and postictal depression (see OVERDOSAGE).
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