Side effects that may occur while taking this medication include: Constipation, Muscle pain, Tenderness or weakness, Lack of energy or fever, Yellowing of the skin or eyes, Headache, Joint pain, Back pain, Stomach pain, Confusion, Memory problems, Swelling, Weight gain, Urinating less than usual or not at all, Gas, Bloating, Stomach upset, Heartburn, Indigestion, Nausea, Diarrhea, Sleep problems (insomnia) If any of these situations worsen or persist, contact your physician immediately. Seek immediate medical help if a serious allergic reaction occurs that may include rash, itching, or swelling.