Antihistamines + Macrolide antibacterials Erythromycin causes terfenadine and astemizole to accumulate in a few individuals, which can lead to life-threatening torsade de pointes arrhythmias. Other macrolides are believed to interact similarly, with the exception of azithromycin and possibly dirithromycin. The makers of mizolastine contraindicate erythromycin, although the evidence for an interaction is poor. There is a slight prolongation of the QT interval with ebastine/erythromycin, and there is an isolated case of torsade de pointes possibly due to spiramycin/mequitazine. Azelastine, cetirizine, desloratadine, fexofenadine, levocabastine, and loratadine seem to be free of clinically relevant interactions with macrolides, although in some cases their serum levels may be raised.