I took omeprazole (Prilosec) for 1 1/2 months but had to switch to Protonix because I developed diarrhea(sp). It did help my symptoms, though. My pharmacist said that GI side effects are common. If your diarrhea is continuing beyond a few days, DEFINITELY get in touch with your doctor. It can be serious if it's not taken care of. You might try a different PPI. With Protonix, so far so good. Sue