Histamine is a substance produced by the body in response to allergic reactions that triggers immune response symptoms such as watery eyes, runny nose, and sneezing. Antihistamines are a class of drugs that block the action of histamine and reduce these symptoms. Older antihistamines had many side effects such as severe drowsiness. Newer antihistamines, called selective H1-receptor antagonists, do not cross into the brain and have fewer side effects. In 2007, the FDA approved Zyrtec, or cetirizine, as an over-the-counter drug to treat allergic rhinitis and chronic urticaria, a skin condition characterized by recurrent hives.
Zyrtec Side Effects
RxList reports that the overall incidence of Zyrtec-related side effects requiring discontinuation of the drug is not different than placebo in large studies. The most common side effects, usually mild to moderate, are sleepiness, fatigue, pharyngitis, dry mouth and dizziness. Cardiac side effects are rare, occurring in less than two percent of patients taking Zyrtec.
When the heart cannot pump enough blood to meet the body's demands, this is called heart failure. Heart failure has many causes, including heart attack, uncontrolled blood pressure, metabolic abnormalities and drug effects. Zyrtec has been linked to cases of heart failure through an unknown mechanism in a very small number of patients. Symptoms of heart failure include shortness of breath, cough and leg swelling and should be reported promptly to a health care provider.
Palpitations and Tachycardia
Palpitations are described as an unpleasant awareness of the heart beating or a fast heart rate, called tachycardia. Palpitations and tachycardia can occur with both normal and abnormal heart rhythms and have been reported in conjunction with the use of Zyrtec. Drugs.com reports these side effects are seen more frequently with Zyrtec-D, a combination of Zyrtec and pseudoephedrine. Pseudoephedrine is a decongestant and has been linked to numerous cardiac side effects.
Hypertension occurs in less than two percent of patients taking Zyrtec and the mechanism of the blood pressure elevation in those patients is unknown. Zyrtec-D has a higher incidence of the hypertension side effect. This is thought to be related to the pseudoephedrine component of the drug. Zyrtec-induced hypertension resolves quickly with discontinuation of the drug.