The most common side effects of this drug are heartburn, gas and upset stomach. Constipation can also occur, but can be prevented if you drink 8 to 12 glasses of fluid each day. Less common, but serious, side effects include inability to move your bowels, unusual bruising, muscle aches and unusual bleeding. Seek immediate medical attention if you experience hives, itching, rash or swelling of the lips, face, throat or tongue, as they are signs of a serious allergic reaction.