The New Antihistamines-Desloratadine and Levocetirizine: A Review

Antihistamines are among the most commonly used medications by allergists and dermatologists worldwide. They are used to treat indications such as rhinitis, urticaria, seasonal allergies, and pruritus, and their potential role in treating the itch and rash of atopic dermatitis remains unclear. However, many antihistamines have the drawback of causing sedation. New antihistamines have been developed and released in recent years to overcome the limitations of older agents.

First generation antihistamines such as hydroxizine are effetive but cause sedation. The initial second generation antihistamines, terfanadine and astemizole, were effective non-sedating medications but had drug interactions that caused cardiac problem and have been pulled from the market in the United States. Later second generation antihistamines, such as loratidine and cetirizine, have been found to be effective in the treatment of allergic rhinitis, and the latter to be effective in the treatment of chronic idiopathic urticaria. More recently, third generation antihistamines have been developed from existing agents (e.g. desloratadine is the active metabolite of loratidine, levocetirizine is the racemically active component of cetirizine, and fexofenadine is a derivative of terfanadine) to increase effectiveness and decrease side effects. Desloratadine has been released in the United States and Europe, while levocetirizine is currently only available in Europe. This article will review over 50 clinical studies and reviews regarding desloratadine and levocetirizine with an overview of their possible dermatological use.