Cetirizine, a second-generation antihistamine, is a major metabolite of hydroxyzine, and a racemic selective H1 receptor inverse agonist used in the treatment of allergies, hay fever, angioedema, and urticaria. Formerly prescription-only in the USA and Canada, cetirizine is now available over-the-counter in both countries as Zyrtec and Reactine, respectively. Zyrtec was the highest-grossing new non-food product of 2008 in the US, generating sales of $315.9 million. It is also available as a generic drug. In Australia and New Zealand, Zyrtec is available over-the-counter in pharmacies and in the UK cetirizine can be sold in limited quantities off-the-shelf in any outlet and is often available in supermarkets. As of 2009, Germany made many generic drugs containing cetirizine available in pharmacies without prescription. Norway, Sweden, Finland, Poland and Israel also recognize Cetirizine as an over-the-counter medicine.
Contributions by James.Spudeman, CheMoBot, and Viriditas.