In the U.S., Terfenadine was superseded by fexofenadine in the 1990s due to the risk of cardiac arrhythmia caused by QT interval prolongation.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
Humans and other mammals
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%
Biochem/physiol Actions Non-sedating second generation H1 histamine receptor antagonist. Mainly metabolized by Cyp3A4, 5, 7. Inhibits CYP2C8. Other Notes Tandem Mass Spectrometry data independently generated by Scripps Center for Metabolomics is available to view or download in PDF. T9652.pdf Tested metabolites are featured on Scripps Center for Metabolomics METLIN Metabolite Database. To learn more, visit sigma.com/metlin.