12 Hour Allergy Relief Side Effects
Generic Name: clemastine
Note: This document contains side effect information about clemastine. Some of the dosage forms listed on this page may not apply to the brand name 12 Hour Allergy Relief.
For the Consumer
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]
Gastrointestinal side effects have included dry mouth and constipation due to anticholinergic effects. This has occurred in up to one-third of patients.[Ref]
Cardiovascular side effects have included hypotension, tachycardia, and palpitations.[Ref]
Ocular effects are due to the anticholinergic effects and may include blurred vision, diplopia, and dry eyes.[Ref]
Genitourinary side effects have included dysuria, urinary hesitancy, decrease in urine flow, and in rare cases, acute urinary retention.[Ref]
Hematologic side effects that have been reported with antihistamines include bone marrow suppression, thrombocytopenia, and aplastic anemia.[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]
At least one case of toxic pustuloderma has been reported during clemastine (the active ingredient contained in 12 Hour Allergy Relief) therapy.[Ref]
Dermatologic side effects have included toxic pustuloderma.[Ref]
1. 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
2. "Letter: Dyskinesia associated with chronic antihistamine use." N Engl J Med 294 (1976): 113
3. Frolund L, Etholm B, Irander K, Johannessen TA, Odkvist L, Ohlander B, Weeke B "A multicentre study of loratadine, clemastine and placebo in patients with perennial allergic rhinitis." Allergy 45 (1990): 254-61
4. "Product Information. Tavist (clemastine)." Sandoz Pharmaceuticals Corporation, East Hanover, NJ.
5. 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
6. Schuller DE, Turkewitz D "Adverse effects of antihistamines." Postgrad Med 79 (1986): 75-86
7. Thach BT, Chase TN, Bosma JF "Oral facial dyskinesia associated with prolonged use of antihistaminic decongestants." N Engl J Med 293 (1975): 486-7
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. Kanoh T, Jingami H, Uchino H "Aplastic anaemia after prolonged treatment with chlorpheniramine ." Lancet 1 (1977): 546-7
11. Deringer PM, Maniatis A "Chlorpheniramine-induced bone-marrow suppression." Lancet 1 (1976): 432
12. Hardin AS "Chlorpheniramine and agranulocytosis ." Ann Intern Med 108 (1988): 770
13. Eisner EV, LaBocki NL, Pinckney L "Chlorpheniramine-dependent thrombocytopenia." JAMA 231 (1975): 735-6
14. Feindkoopmans A, Vandervalk PGM, Steijlen PM, Vandekerkhof PCM "Toxic pustuloderma associated with clemastine therapy." Clin Exp Dermatol 21 (1996): 293-5
Some side effects of 12 Hour Allergy Relief may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
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- Drug class: antihistamines
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