Desloratadine
H1 antihistamine · also known as Clarinex, desloratadine
Second-generation H1 antihistamine; the active metabolite of loratadine, and the one member of this class that requires a prescription.
- How it relates to mast cells
- Acts after mast-cell mediators are released
- Types of studies cited
- Randomised controlled trial
- Approved in the US for
- allergic rhinitis and chronic idiopathic urticaria
What this relationship means: Acts after mast-cell mediators are released rather than stabilising the mast cell itself. This includes treatments that block mediator receptors, degrade a mediator, or oppose the physiology of an acute reaction. It describes where the intervention acts, not its clinical importance.
Mechanism of action
Mechanism of action
Desloratadine is the active metabolite of loratadine and a second-generation H1 receptor antagonist. It blocks the H1 receptor downstream of mediator release.
It is the only member of this class listed here that is dispensed on prescription in the United States rather than over the counter. That difference is regulatory: the others reached over-the-counter status through the FDA’s switch process, and this one has not. Nothing in the evidence cited here distinguishes it clinically from the rest of the class.
Sources
- Desloratadine US prescription label Drug label · link checked 25 Aug 2026
- Cetirizine versus hydroxyzine and placebo in chronic idiopathic urticaria Peer-reviewed study 1996 PMID 8893110 · link checked 21 Aug 2026
- Mast Cell Activation Syndrome and Mastocytosis: Initial Treatment Options and Long-Term Management Review article 2019 PMID 30961835 · link checked 20 Aug 2026