Pharmacodynamic interactions between terfenadine and other potentially arrhythmogenic drugs may occur e.g.: − other antihistamines that prolong QT interval − antiarrhythmics, in particular those of class I and III − bepridil − trimethoprime − sparfloxacin − cisapride − tricyclic antidepressants, neuroleptics, lithium − probucol − pentamidine − halofantrine