Seldane Adverse Reactions

Mike Kelly
Pharmacy Intern

Seldane (terfenadine) has continued to get nasty press. The FDA has recently initiated a process that could result in the withdrawal of this drug from the marketplace.

Recently Seldane's patent has expired and several companies are now producing generics of this drug which may (due to lower cost) increase the use of this drug.

The manufacturer of Seldane, Hoechst Marion Roussel, has introduced Allegra (fexofendine), an active metabolite of terfenadine, which does not have the potential adverse reactions. This joins Claritin (loratadine) as another non-sedating antihistamine. Fexofendine is dosed at one tablet (60mg) twice daily for patients 12 years and older.

The mechanism of terfenadine induced cardiotoxicity is unclear but may be related to inhibition of potassium influx during repolarization.

Terfenadine and Hisminal (astemizole) are contraindicated in patients taking Ketoconazole, Itraconazole, Erythromycin, Clarithromycin, Troleandomycin, and in patients with significant hepatic dysfunction. Cardiovascular events, cardiac arrest, torssades de pointes, and death have occurred.

Alternative therapy includes the use of over-the-counter (OTC) antihistamines such as Benadryl (diphenhydramine), Chlortrimeton (chlorpheniramine), and Tavist-1 (clemastine).