Loratadine is a second-generation H1 histamine antagonist drug used to treat allergies. In structure, it is closely related to tricyclic antidepressants, such as imipramine, and is distantly related to the atypical antipsychotic quetiapine. Loratadine is indicated for the symptomatic relief of allergy such as hay fever, urticaria, and other skin allergies For allergic rhinitis, loratadine is effective for both nasal and eye symptoms. Loratadine could be also used to treat mild to moderate pain from headaches. Loratadine is a tricyclic antihistamine, which acts as a selective inverse agonist of peripheral histamine H1-receptors. Histamine is responsible for many features of allergic reactions. Loratadine is given orally, is well absorbed from the gastrointestinal tract, and has rapid first-pass hepatic metabolism; it is metabolized by isoenzymes of the cytochrome P450 system, including CYP3A4, CYP2D6, and, to a lesser extent, several others.
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