Drug Groups

approved

Description

Loratadine is a derivative of azatadine and a second-generation histamine H1 receptor antagonist used in the treatment of allergic rhinitis and urticaria. Unlike most classical antihistamines (histamine H1 antagonists) it lacks central nervous system depressing effects such as drowsiness. [PubChem]

Indication

A self-medication that is used alone or in combination with pseudoephedrine sulfate for the symptomatic relief of seasonal allergic rhinitis. Also used for the symptomatic relief of pruritus, erythema, and urticaria associated with chronic idiopathic urticaria in patients (not for children under 6 unless directed by a clincian).

Pharmacology

Loratadine is a long acting second generation antihistamine that is similar in structure to cyproheptadine and azatadine. The pharmacology of loratadine is similar to other antihistamines, but unlike other H₁-blockers, loratidine is shown to exhibit competitive, specific, and selective antagonism of H₁ receptors. The exact mechanism of this interaction is unknown, but disposition of the drug suggests that loratadine's prolonged antagonism of histamine may be due to the drug's slow dissociation from the receptor or the formation of the active metabolite, desloratadine. Loratadine does not penetrate the CNS effectively and has a low affinity for CNS H₁-receptors.

Toxicity

somnolence, tachycardia, and headache LD₅₀=mg/kg (orally in rat)

Affected Organisms

Biotransformation

Hepatic

Absorption

Rapidly absorbed following oral administration (40% bioavailability)

Half Life

8.4 hours

Protein Binding

97-99%

References

External Links