Cetirizine

Cetirizine, sold under the brand name Zyrtec among others, is a second generation antihistamine used to treat allergic rhinitis (hay fever), dermatitis, and urticaria. It is taken by mouth. Effects generally begin within an hour and last for about a day. The degree of benefit is similar to other antihistamines such as diphenhydramine. 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. Serious side effects may include aggression and angioedema. Use in pregnancy appears safe, but use during breastfeeding is not recommended. The medication works by blocking histamine H1 receptors, mostly outside the brain. It was patented in 1981 and came into medical use in 1987. It is available as a generic medication. A month's supply in the United Kingdom costs the NHS about £0.70 as of 2019. In the United States the wholesale cost of this amount is about US$2.50. In 2016 it was the 74th most prescribed medication in the United States, with more than 10 million prescriptions. 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, more efficiently than any other second-generation antihistamine. 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.In the UK up to 30 tablets of 10mg are on the general sales list (of pharmaceuticals) and can be purchased without a prescription and without pharmacist supervision. Commonly reported side effects of cetirizine include headache (16%), dry mouth (5.7%), drowsiness (5–20%), and fatigue (5.6%), while more serious but rare side effects include cardiac failure, tachycardia, and edema. Discontinuing cetirizine after prolonged use (typically, use beyond six months) may result in generalized itching.