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What is Desloratadine and explain in detail?
Desloratadine (trade names Clarinex and Aerius) is a tricyclic H1 inverse agonist that is used to treat allergies.  It is an active metabolite of loratadine.
It was patented in 1984 and came into medical use in 2001.

Medical uses
Desloratadine is used to treat allergic rhinitis,  nasal congestion and chronic idiopathic urticaria (hives).  It is the major metabolite of loratadine and the two drugs are similar in safety and effectiveness. Desloratadine is available in many dosage forms and under many trade names worldwide.An emerging indication for desloratadine is in the treatment of acne, as an inexpensive adjuvant to isotretinoin and possibly as maintenance therapy or monotherapy.

Side effects
The most common side-effects are fatigue (1.2%), dry mouth (3%), and headache (0.6%).

Interactions
Co-administration with erythromycin, ketoconazole, azithromycin, fluoxetine or cimetidine resulted in elevated blood plasma concentrations of desloratadine and its metabolite 3-hydroxydesloratadine in studies. However, no clinically relevant changes were observed.

Pharmacology
Pharmacodynamics
Desloratadine is a selective H1-antihistamine which functions as an inverse agonist at the histamine H1 receptor.At very high doses, is also an antagonist at various subtypes of the muscarinic acetylcholine receptors. This effect is not relevant for the drugs action at therapeutic doses.

Pharmacokinetics
Desloratadine is well absorbed from the gut and reaches highest blood plasma concentrations after about three hours