Mechanism of Action Desloratadine is a long-acting tricyclic histamine antagonist with selective H1-receptor histamine antagonist activity.Receptor binding data indicate that at a concentration of 2–3 ng/m L (7 nanomolar), desloratadine shows significant interaction with the human histamine H1-receptor.
These medications decrease gastric acid secretion in the stomach by antagonizing the effects of histamine at H2 receptors found in gastrointestinal parietal cells.
6 Antihistamine medications block or reduce histamine-mediated effects at one of four identified histamine receptors (see Table 1 below).
These include the first-generation H1 antagonists, or sedating antihistamines (eg, diphenhydramine, chlorpheniramine), and second-generation H1 receptor blockers, or nonsedating antihistamines (eg, loratadine, cetirizine).
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Educating older patients and their caregivers is especially important because of the widespread OTC availability of these antihistamines.