US regulators have issued a warning on bowel cleansing drugs. These drugs which are used to clear the bowels before colonoscopy could harm kidneys of the patient.

The FDA has declared that it would issue a black-box warning on the oral sodium phosphate products Visicol and OsmoPrep. The step would be initiated to warn consumers about the risk of acute phosphate nephropathy -- a type of severe kidney injury which can be caused by these drugs. This could lead to permanent kidney damage.

"The FDA has received reports of 20 unique cases of kidney injury associated with the use of OsmoPrep," Dr. Joyce Korvick, deputy director of FDA's Division of Gastroenterology Products at the Center for Drug Evaluation and Research, said during an afternoon teleconference. Out of these cases, three cases were proved to be cases of acute phosphate nephropathy. The injury to the kidneys, in the said cases, occurred within a few hours of the drug intake whereas in others it took up to 21 days.

The FDA has issued guidelines to the drug manufacturing company, Salix Pharmaceuticals of Morrisville, N.C., to make people aware of the dangers associated with the drug so that they are aware of the risk of kidney injury, and to conduct a post-marketing clinical trial to gauge the risk of injury.