Nausea & vomiting. The common side-effects of Erythromycin are nausea, vomiting, sharp abdominal pain, cramps and diarrhea. This also occurs commonly with the related Clarithromycin (biaxin). Azithromycin (zithromax) may trigger these same symptoms but its does so much less frequently. Many people who have GI problems with Erythromycin tolerate zithromax just fine.