Drug Groups

approved; withdrawn

Description

In the U.S., Terfenadine was superseded by fexofenadine in the 1990s due to the risk of cardiac arrhythmia caused by QT interval prolongation.

Indication

For the treatment of allergic rhinitis, hay fever, and allergic skin disorders.

Pharmacology

Terfenadine, an H1-receptor antagonist antihistamine, is similar in structure to astemizole and haloperidol, a butyrophenone antipsychotic. The active metabolite of terfenadine is fexofenadine.

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)

Affected Organisms

Biotransformation

Hepatic

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%

Half Life

3.5 hours

Protein Binding

70%

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