I have been on Zegerid for quite a while for GERD and hiatal hernia. I am currently on antibiotics and had drug reactions 2 nights in a row. The symptoms were jittery feeling, sleeplessness, feeling like you can't breathe right, chest discomfort. Those two nights I took Zegerid and then the antibiotic Keflex within a half hour of each other. Last night I did not take my Zegerid and it did not happen. Anyone on antibiotics please be careful--my doctor had not even heard of it reacting with Keflex.