DRUG CLASS AND MECHANISM: Desloratadine is an oral, long-acting antihistamine that is similar chemically to loratadine (Claritin). It is used to treat the symptoms caused by histamine. Histamine is a chemical that is responsible for many of the signs and symptoms of allergic reactions, for example, swelling of the lining of the nose, sneezing, and itchy eyes. Histamine is released from histamine-storing cells (mast cells) and then attaches to other cells that have receptors for histamine. The attachment of the histamine to the receptors causes the cell to be "activated," releasing other chemicals which produce the effects that we associate with allergy.
Both drugs are produced by the Schering Corporation, whose ads signify a desperate attempt to maintain market share. The patent is about to run out on Claritin, the most profitable antihistamine of all time with annual sales of more than $2 billion. ...
Desloratadine blocks one type of receptor for histamine (the H1 receptor) and thus prevents activation of H1 receptor-containing cells by histamine. Desloratadine does not readily enter the brain from the blood and, therefore, causes less drowsiness (sedation). It is a member of a small family of non-sedating antihistamines which includes loratadine (Claritin), cetirizine (Zyrtec), and azelastine (Astelin). Desloratadine was approved by the FDA in December, 2001.
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