FDA puts black box warning on bowel-clearing drugs

Federal health officials said they will add the sternest safety warnings available to drugs used before colonoscopies, following reports of kidney damage in several patients.The Food and Drug Administration said it has received more than 20 reports of a serious form of kidney failure among patients taking the bowel-cleansing drugs, known as oral phosphate products.The new boxed warning label will apply to Visicol and OsmoPrep — both prescription tablets made by Salix Pharmaceuticals. The label warns that the drugs should be used with caution in patients older than 55, those who suffer from dehydration and kidney disease, and those who take medications that affect the kidneys. Regulators said they are also concerned about the risks of over-the-counter bowel cleansers, such as Fleet Phospho-soda, made by C.B. Fleet Company Inc.

Officials said kidney damage can occur within days or weeks of using the drugs, but symptoms — such as lethargy, drowsiness and swelling — may not appear until much later. FDA is requiring Salix to distribute a medication guide warning patients about the risks of the drugs. The company also must conduct a follow-up study looking at which patients are most vulnerable to kidney damage.