Clemastine fumarate is an antihistamine used to treat seasonal allergy symptoms such as rhinitis and itchy eyes, and to treat uncomplicated skin rashes and angioedema. This antihistamine is available only by prescription because it has strong anticholinergic (atropine-like drying effects) and sedative effects. Potential adverse side effects are many, affecting multiple body systems.
Central Nervous System Side Effects
Central nervous system side effects include headache, drowsiness and fatigue, dizziness with impaired coordination, confusion and vertigo. Clemastine fumarate can also cause feelings of nervousness and anxiety, tremor, tingling and weakness in the hands, and even hysteria. Blurred vision and diplopia (double vision) may also occur. The National Institute of Health (NIH) reports that a potentially life-threatening adverse side effect is convulsions.
Cardiovascular Side Effects
Clemastine fumarate can affect heart rate to include bradycardia (slow) or tachycardia (fast). Irregular heart rhythms such as extra beats and palpitations may also occur. Clemastine fumarate may also lower blood pressure, causing hypotension.
Gastrointestinal Side Effects
Nausea, vomiting and diarrhea may occur. Appetite can be affected by either anorexia (loss of appetite) or by an increased appetite leading to weight gain. Clemastine fumarate may also cause constipation in some patients.
Genitourinary Side Effects
Clemastine fumarate can cause many genitourinary side effects ranging from urinary frequency and painful urination to urinary retention. Use of this antihistamine can decrease libido and cause impotence.
Hematologic Side Effects
The NIH reports that clemastine fumarate can lower production of platelets and white blood cells, resulting in thrombocytopenia and leukopenia. Red blood cells may also be affected, inducing hemolytic anemia, which is a condition in which red blood cells are prematurely destroyed.
Respiratory System Effects
Patients taking the antihistamine clemastine fumarate may experience chest tightness, wheezing and dry mouth, throat and nasal passages. Thickening of bronchial secretions will also occur because of the drying effects. It is important to stay hydrated, and use of a humidifier may help alleviate these symptoms.
General Side Effects
A generalized rash and itching may occur when taking clemastine fumarate. Sensitivity to light may also occur, and excessive perspiration and chills have been reported by patients. Clemastine fumarate, like all other medications, has the potential to cause anaphylactic shock. Patients with known or suspected sensitivity to clemastine fumarate and its active and inactive ingredients, as well as any medications in this antihistamine class, should not take clemastine fumarate.
Warnings
There is a great increase in the sedative effects of clemastine fumarate when taken with other medications that cause central nervous system depression (sedation), so caution is advised when taking multiple medications. Your physician should be notified of all medications being taken to avoid drug interactions. Alcohol should be avoided.
References
- National Institute of Health Daily Med Sheet
- Karch, A. M. (2008). 2008 Lippincott's Nursing Drug Guide. New York: Lippincott Williams & Wilkins
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