Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Pentasa can cause some of the symptoms you are experiencing like headaches, heartburn, stomach discomfort, nausea and diarrhea. Sometimes it may also worsen Crohn disease. If you think it is worsening your bowel symptoms (bloody diarrhea, worse abdominal pain) you will need to let your doctor know soon and he should decide on possibly stopping it and on further treatment. Crohn disease needs to be treated as well, as it may also cause symptoms that are bothersome so a good weighting of the benefits against the side effects should be done. There are other drugs that can be used to treat Crohn (like steroids or drugs that effect the immune response like azathioprine or methotrexate) but your doctor has to balance benefits and risks with these drugs also. You will need to get iron and folic acid supplements due to the increased loose of iron with stools due to chronic bleeding. This is the case especially if you have anemia in CBC. Hope I have answered your query. Let me know if I can assist you further. Kind regards, Antoneta Zotaj, MD