Cetirizine

Cetirizine is a second-generation peripherally selective antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria (hives).^[11] It is taken by mouth.^[12] Effects generally begin within thirty minutes and last for about a day.^[12] The degree of benefit is similar to other antihistamines such as diphenhydramine, which is a first-generation antihistamine.^[12]

Common side effects include sleepiness, dry mouth, headache, and abdominal pain.^[12] 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.^[13][11] Compared to other second-generation antihistamines, cetirizine can cause drowsiness.^[13] Among second-generation antihistamines, cetirizine is more likely than fexofenadine and loratadine to cause drowsiness.^[13]

Use in pregnancy appears safe, but use during breastfeeding is not recommended.^[14] The medication works by blocking histamine H₁ receptors, mostly outside the brain.^[12]

Cetirizine can be used for paediatric patients. The main side effect to be cautious about is somnolence.^[15]

It was patented in 1983^[16][17] and came into medical use in 1987.^[18] It is on the World Health Organization's List of Essential Medicines.^[19] It is available as a generic medication.^[11] In 2022, it was the 43rd most commonly prescribed medication in the United States, with more than 13 million prescriptions.^[20][21]