| Indication | For the treatment of allergic rhinitis, hay fever, and allergic skin disorders. |
| Pharmacodynamics | Terfenadine, an H1-receptor antagonist antihistamine, is similar in structure to astemizole and haloperidol, a butyrophenone antipsychotic. The active metabolite of terfenadine is fexofenadine. |
| Mechanism of action | Terfenadine competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of terfenadine to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity. As the drug does not readily cross the blood-brain barrier, CNS depression is minimal. |
| Absorption | On the basis of a mass balance study using 14C labeled terfenadine the oral absorption of terfenadine was estimated to be at least 70% |
| Volume of distribution | Not Available |
| Protein binding | 70% |
| Metabolism | Hepatic |
| Route of elimination | Not Available |
| Half life | 3.5 hours |
| Clearance | Not Available |
| Toxicity | Mild (e.g., headache, nausea, confusion), but adverse cardiac events including cardiac arrest, ventricular arrhythmias including torsades de pointes and QT prolongation have been reported. LD50=mg/kg (orally in mice) |
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