Cetirizine

Cetirizine is a second-generation peripherally selective antihistamine used to treat allergic rhinitis (hay fever), dermatitis, urticaria (hives), and runny nose. It is taken by mouth. Effects generally begin within thirty minutes and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation antihistamine. Common side effects include sleepiness, dry mouth, headache, and abdominal pain. The degree of sleepiness that occurs is generally less than with first-generation antihistamines because second-generation antihistamines are more selective for the H1 receptor. Compared to other second-generation antihistamines, cetirizine can cause drowsiness. Among second-generation antihistamines, cetirizine is more likely than fexofenadine and loratadine to cause drowsiness, but cetirizine shows superior efficacy in the histamine induced wheal and flare paradigm and tends to produce slightly greater clinical symptom relief than fexofenadine, which in turn tends to produce greater symptom relief than loratadine, meanwhile loratadine was unable to show significant superiority over placebo. Use in pregnancy appears safe, but use during breastfeeding is not recommended. The medication works by blocking histamine H1 receptors, mostly outside the brain. Cetirizine can be used for paediatric patients. The main side effect to be cautious about is somnolence. It was patented in 1983 by UCB and came into medical use in 1987. Cetirizine is a therapeutic alternative on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2023, it was the 55th most commonly prescribed medication in the United States, with more than 11 million prescriptions.

Medical uses

Allergies Cetirizine's primary indication is for hay fever and other allergies. Because the symptoms of itching and redness in these conditions are caused by histamine acting on the H1 receptor, blocking those receptors temporarily relieves those symptoms. Cetirizine is also commonly prescribed to treat acute and (in particular cases) chronic urticaria (hives), more efficiently than any other second-generation antihistamine.

Available forms Cetirizine is available over-the-counter in the US in the form of 5 and 10 mg tablets. A 20 mg strength is available by prescription only. It is also available as a 1 mg/mL syrup for oral administration by prescription. In the UK, up to 30 tablets of 10 mg are on the general sales list (of pharmaceuticals) and can be purchased without a prescription and pharmacist supervision. The drug can be in the form of tablets, capsules or syrup.

Adverse effects Commonly reported side effects of cetirizine include headache, dry mouth, drowsiness, and fatigue, while more serious, but rare, adverse effects reported include tachycardia and edema.

Pruritus after discontinuation of cetirizine Discontinuing cetirizine after prolonged use (typically, use beyond six months) may result in rare but severe generalized itching, also called pruritus. The itching generally occurs in patients who stop cetirizine after using the medication daily, and begins within a few days of stopping the medication. Although the mechanism by which cetirizine cessation causes itching is unknown, a case analysis by the FDA supports a causal relationship. The US Food and Drug Administration (FDA) analyzed cases of pruritus after stopping cetirizine in the FDA Adverse Event Reporting System (FAERS) database and medical literature through April 2017. Their report noted that some patients indicated the itchiness impacted their ability to work, sleep or perform normal daily activities. On 16 May 2025, the FDA issued a Drug Safety Communication regarding the pruritus that can occur after discontinuing long-term use of cetirizine and levocetirizine. The FDA communication reports that symptoms would typically go away after restarting the medicine, and in some individuals were addressed by weaning off. No specific schedule for weaning is provided in the drug information for cetirizine.

Pharmacology

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