Key takeaways
Erythromycin (Ery-tab, E.E.S.) and azithromycin (Zithromax) are both macrolide antibiotics used to treat bacterial infections, such as respiratory and skin infections. They also share an off-label use for treating gastroparesis (slowed movement through the stomach and intestines). Both medications come as oral tablets and liquid forms and are available as lower-cost generics. However, they differ in several ways. Erythromycin is typically taken multiple times a day, while azithromycin is typically taken once daily. And you usually need to take azithromycin for a shorter amount of time. Erythromycin also seems more likely to cause stomach issues, such as nausea and diarrhea. Both medications can can cause QT prolongation, a heart rhythm problem, but this side effects is rare.
