1. a history of cancer 2. a history of intestinal surgery or malabsorption 3. a history of renal insufficiency 4 a history of allergy or hypersensitivity to salicylates or aminosalicylates 5. evidence of clinically significant organic or psychiatric disease on medical history or physical examination that, in the Investigator's opinion, would prevent the patient from completing the study or would jeopardize the patient's safety 6. a creatinine clearance of < or =30 mL/minute at screening, estimated by serum creatinine using the Traub & Johnson equation for calculating pediatric creatinine clearance.