Correct electrolyte abnormalities eg, hypernatremia, hyperphosphatemia, hypokalemia, or hypocalcemia before treatment. Patients who are taking medications that increase the risk for fluid & electrolyte disturbances or may increase the risk of arrythmias, seizure, or renal impairment. Hydrate adequately before, during, & after treatment. Consider pre-dose & post-colonoscopy ECGs in patients at increased risk of serious cardiac arrythmias. Patients w/ severe active ulcerative colitis. Consider performing baseline & post-colonoscopy labs (phosphate, Ca, K, Na, creatinine, & BUN) in patients w/ renal impairments. Severe renal impairment (CrCl <30 mL/min).