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Pharmacology: Pharmacodynamics: Desloratadine is a non-sedating long-acting histamine antagonist with potent, selective peripheral H1-receptor antagonist activity. Desloratadine has demonstrated antiallergic, antihistaminic, and anti-inflammatory activity.
Pharmacodynamic Properties: After oral administration, desloratadine selectively blocks peripheral histamine H1-receptors because the drug is effectively excluded from entry to the central nervous system (CNS).
In addition to antihistaminic activity, desloratadine has demonstrated antiallergic and anti-inflammatory activities from numerous studies. These studies have shown that desloratadine inhibit the broad cascade of events that initiate and propagate allergic inflammation including, the release of proinflammatory cytokines including IL-4, IL-6, IL-8, IL-13, the release of important proinflammatory chemokines such as RANTES (Regulated upon Activation, Normal T-cell Expressed and Secreted), superoxide anion production by activated polymorphonuclear neutrophils, eosinophil adhesion and chemotaxis, the expression of the adhesion molecules such as P-selectin, IgE-dependent release of histamine, prostaglandin (PGD2), and leukotriene (LTC4), the acute allergic bronchoconstrictor response and allergic cough in animal models.
Pharmacokinetics: Desloratadine plasma concentrations can be detected within 30 minutes of desloratadine administration. Desloratadine is well absorbed with maximum concentration achieved after approximately 3 hours; the terminal phase half-life is approximately 27 hours. The degree of accumulation of desloratadine was consistent with its half-life (approximately 27 hours) and a once daily dosing frequency. In adults and adolescents, the bioavailability of desloratadine was dose proportional over the range of 5 mg to 20 mg.
Desloratadine is moderately bound (83%-87%) to plasma proteins. There is no evidence of clinically relevant drug accumulation following once daily dosing of desloratadine (5 mg to 20 mg) for 14 days.
The enzyme responsible for the metabolism of desloratadine has not been identified yet, and therefore some interactions with other drugs cannot be fully excluded. Desloratadine does not inhibit CYP3A4 or CYP2D6 and is neither a substrate nor an inhibitor of P-glycoprotein.
In a single dose trial using a 7.5 mg dose of desloratadine, there was no effect of food (high-fat, high caloric breakfast) on the disposition of desloratadine. In another study, grapefruit juice had no effect on the disposition of desloratadine.
