This medication may cause stomach upset, diarrhea, nausea, headache or vomiting during the first few days as your body adjusts to the medication. If these symptoms persist or become severe, inform your doctor. This may cause urine to be orange-brown in color. This is not a cause for concern and will disappear when the medication is stopped. Rarely, this medication can cause serious, even fatal, side effects such as a severe peeling skin rash known as Stevens- Johnson syndrome, blood disorders (e.g., agranulocytosis, aplastic anemia), or liver damage. Seek immediate medical attention if you develop any of the following symptoms: skin rash or blisters, unusual fatigue, persistent sore throat or fever, yellowing eyes or skin, dark urine, abdominal pain. In the unlikely event you have an allergic reaction to this drug, seek immediate medical attention. Symptoms of an allergic reaction include: rash, itching, swelling, dizziness, trouble breathing. If you notice other effects not listed above, contact your doctor or pharmacist.