About desloratadinesecond generation long-acting tricyclic h1 antagonist, antihistamine.mechanism of action of desloratadinethis second generation antihistamine has a selective peripheral h1-antagonist action.desloratadine competes with free histamine for binding at h1-receptors in the gi tract, uterus, large blood vessels, and bronchial smooth muscle. this inhibit the action of histamine, which subsequently leads to temporary relief of the negative symptoms brought by histamineindications for desloratadine1. hay fever 2. watery eyes 3. runny nose 4. itching eyes 5. sneezing 6. hives 7. decongestant typical dosage for desloratadineadult (general dose)- 5mg/day children (>12yrs)-same as adult