[1] It was superseded by fexofenadine in the 1990s due to the risk of a particular type of disruption of the electrical rhythms of the heart (specifically cardiac arrhythmia caused by QT interval prolongation) and has been withdrawn from markets worldwide.

In larger plasma concentrations, it may lead to toxic effects on the heart's rhythm (e.g. ventricular tachycardia and torsades de pointes).

[1][5] In June 1990, evidence of serious ventricular arrhythmias among those taking Seldane prompted the FDA to issue a report on the risk factors associated with concomitant use of the drug with macrolide antibiotics and ketoconazole.

[1] Two months later, the FDA required the manufacturer to send a letter to all physicians, alerting them to the problem; in July 1992, the existing precautions were elevated to a black box warning[1] and the issue attracted mass media attention in reports that people with liver disease or who took ketoconazole, an antifungal agent, or the antibiotic erythromycin, could suffer cardiac arrhythmia if they also took Seldane.

[5] Seldane (and Seldane-D, terfenadine combined with the decongestant pseudoephedrine) were removed from the U.S. market by their manufacturer in late 1997 after the FDA approval of Allegra-D (fexofenadine/pseudoephedrine).