Desloratadine is a biologically active metabolite of the second-generation antihistamine loratadine. Desloratadine is a highly selective peripheral H1 receptor antagonist that is significantly more potent than loratadine. Results of in vitro and in vivo studies have suggested that desloratadine has anti-allergic effects that are unrelated to its ability to antagonise the effects of histamine. Desloratadine inhibits the expression of cell adhesion molecules, inhibits the generation and release of inflammatory mediators and cytokines, attenuates eosinophil chemotaxis, adhesion and superoxide generation. Studies in animals indicate that desloratadine does not cross the blood-brain barrier and therefore does not cause sedation and does not impair cognition or psychomotor performance. Desloratadine has an excellent overall safety profile. It has no effect on QRS and QTc intervals and does not cause arrhythmias. Desloratadine is not associated with any significant changes in gastrointestinal function. In clinical studies, oral desloratadine is rapidly absorbed and bioavailability is not affected by ingestion with food or grapefruit juice. The half-life of desloratadine in humans is 27 h; the linear kinetic profile is unaltered by race or gender. Desloratadine is not a substrate for P-glycoprotein or organic anion transport polypeptide and the drug does not appear to be metabolised to a significant extent by the cytochrome P450 CYP3A4 pathway. It therefore may be safely administered with ketoconazole, erythromycin, fluoxetine, or azithromycin. Clinically, desloratadine effectively controls both nasal and non-nasal symptoms of seasonal allergic rhinitis (SAR), including nasal congestion. Desloratadine also provides significant relief of SAR symptoms in patients with co-existing asthma and is effective in the treatment of chronic idiopathic urticaria. Desloratadine improves quality of life and is well-tolerated.
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