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Clemastine Side Effects

Medically reviewed by Last updated on Jan 24, 2022.

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

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]


Dermatologic side effects have included toxic pustuloderma.[Ref]

At least one case of toxic pustuloderma has been reported during clemastine therapy.[Ref]


1. Ralph JW, Crane R, Heurich AE, Shepherd DA, Thomas JS "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

3. Bosma JF, Chase TN, Thach BT "Oral facial dyskinesia associated with prolonged use of antihistaminic decongestants." N Engl J Med 293 (1975): 486-7

4. Schuller DE, Turkewitz D "Adverse effects of antihistamines." Postgrad Med 79 (1986): 75-86

5. Etholm B, Frolund L, Ohlander B, Johannessen TA, Irander K, Weeke B, Odkvist L "A multicentre study of loratadine, clemastine and placebo in patients with perennial allergic rhinitis." Allergy 45 (1990): 254-61

6. "Product Information. Tavist (clemastine)." Sandoz Pharmaceuticals Corporation (2001):

7. Petryk L, Chang CT, Gelbert MB, Schran HF, Oconnor R "The pharmacokinetics and bioavailability of clemastine and phenylpropanolamine in single-component and combination formulations." J Clin Pharmacol 36 (1996): 911-22

8. Batouli AR, Sorrentino JV, Turner RB, Rogers J, Gwaltney JM, OConnor RR, Sperber SJ "Effectiveness of clemastine fumarate for treatment of rhinorrhea and sneezing associated with the common cold." Clin Infect Dis 25 (1997): 824-30

9. Edelman DA, Turner RB, Park J, Paul RA, Gwaltney JM, Oconnor RR "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, Steijlen PM, Vandervalk PGM, Vandekerkhof PCM "Toxic pustuloderma associated with clemastine therapy." Clin Exp Dermatol 21 (1996): 293-5

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.