Contac 12 Hour Allergy Side Effects
Generic name: clemastine
Medically reviewed by Drugs.com. Last updated on Jan 24, 2022.
Note: This document contains side effect information about clemastine. Some dosage forms listed on this page may not apply to the brand name Contac 12 Hour Allergy.
Applies to clemastine: oral oral solution, oral tablets.
Side effects include:
Sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, thickening of bronchial secretions.
For Healthcare Professionals
Applies to clemastine: compounding powder, oral syrup, oral tablet.
Nervous system side effects have included central nervous system depression which has commonly resulted in drowsiness, dizziness, and headache. Dyskinesias have rarely been reported following chronic use of antihistamines.[Ref]
Nearly all patients experience drowsiness. This drowsiness may subside in some patients with extended use. Patients should be warned against driving, as well as concomitant ingestion with alcohol and other sedative-hypnotic drugs.
Few cases of dyskinesias and tremors, often of the face, have been reported in patients whose chronic use of antihistamines extended over a period of 3 to 10 years. Some of these cases were only partially relieved by discontinuation of the drug. Haloperidol was successful in relieving symptoms.[Ref]
Ocular effects are due to the anticholinergic effects and may include blurred vision, diplopia, and dry eyes.[Ref]
A fatal case of agranulocytosis has been reported in a patient taking chlorpheniramine, pseudoephedrine, acetaminophen, dextromethorphan, phenylpropanolamine, and aspirin. Chlorpheniramine was felt to be the cause.[Ref]
Respiratory side effects have included thickening of bronchial secretions, wheezing, and tightness in the chest.[Ref]
Dermatologic side effects have included toxic pustuloderma.[Ref]
At least one case of toxic pustuloderma has been reported during clemastine therapy.[Ref]
More about Contac 12 Hour Allergy (clemastine)
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1. Thomas JS, Heurich AE, Ralph JW, Crane R, Shepherd DA "Double-blind, controlled study of clemastine fumarate, chlorpheniramine and placebo in patients with seasonal allergic rhinitis." Ann Allergy 38 (1977): 169-74
2. "Letter: Dyskinesia associated with chronic antihistamine use." N Engl J Med 294 (1976): 113
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6. "Product Information. Tavist (clemastine)." Sandoz Pharmaceuticals Corporation (2001):
7. Schran HF, Petryk L, Chang CT, Oconnor R, Gelbert MB "The pharmacokinetics and bioavailability of clemastine and phenylpropanolamine in single-component and combination formulations." J Clin Pharmacol 36 (1996): 911-22
8. Turner RB, Sperber SJ, Sorrentino JV, OConnor RR, Rogers J, Batouli AR, Gwaltney JM "Effectiveness of clemastine fumarate for treatment of rhinorrhea and sneezing associated with the common cold." Clin Infect Dis 25 (1997): 824-30
9. Gwaltney JM, Park J, Paul RA, Edelman DA, Oconnor RR, Turner RB "Randomized controlled trial of clemastine fumarate for treatment of experimental rhinovirus colds." Clin Infect Dis 22 (1996): 656-62
10. Hardin AS "Chlorpheniramine and agranulocytosis ." Ann Intern Med 108 (1988): 770
11. Eisner EV, LaBocki NL, Pinckney L "Chlorpheniramine-dependent thrombocytopenia." JAMA 231 (1975): 735-6
12. Kanoh T, Jingami H, Uchino H "Aplastic anaemia after prolonged treatment with chlorpheniramine ." Lancet 1 (1977): 546-7
13. Deringer PM, Maniatis A "Chlorpheniramine-induced bone-marrow suppression." Lancet 1 (1976): 432
14. Feindkoopmans A, Vandervalk PGM, Steijlen PM, Vandekerkhof PCM "Toxic pustuloderma associated with clemastine therapy." Clin Exp Dermatol 21 (1996): 293-5
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Some side effects may not be reported. You may report them to the FDA.