Last year, a Medical Letter article reviewing colonoscopy preparations warned that oral sodium phosphate preparations, such as Fleet Phospho-Soda solution and Visicol tablets, could cause significant electrolyte disturbances and, rarely, renal failure (Med Lett Drugs Ther 2005; 47:53). A subsequent report documented acute phosphate nephropathy and renal failure in 21 patients who had used sodium phosphate before colonoscopy (GS Markowitz et al. J Am Soc Nephrol 2005; 16:3389). Seventeen of these patients were women and 14 were taking an angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB). The FDA recently issued an alert advising against use of oral sodium phosphate in patients with kidney disease or uncorrected electrolyte abnormalities and urges caution in patients taking drugs that may affect renal function such as diuretics, NSAIDs, ACE inhibitors or ARBs.