Colonoscopy prep pills carry kidney risk
In the old days — the late 20th century, that is — you had to drink a gallon of a special salty liquid to cleanse your bowels in basically one sitting. So patients cheered when tasteless tablets that would accomplish the same thing became available in 2000.
But last week, the Food and Drug Administration tempered that joy by adding a "black box" warning — the sternest warning possible — to the two prescription bowel cleansers that come in tablet form. The new warning stems from reports of kidney damage in patients who took the pills, which contain sodium phosphate, in preparation for a colonoscopy.
Also, the FDA, which can require warnings only on prescription drugs, said no over-the-counter sodium phosphate products should be used for bowel-cleansing. That led C.B. Fleet Co. to announce a voluntary recall of Phospho-soda, a non-prescription laxative that in larger doses has been used for bowel-cleansing.
The FDA says prescription Visicol, approved in 2000, and its successor, OsmoPrep, approved in 2006, should be used with caution by people over 55; those who are dehydrated; those who suffer from kidney disease, acute colitis or delayed bowel emptying; and people on medicines that affect kidney function. Medicines include diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers and, maybe, ibuprofen and other non-steroidal anti-inflammatory drugs.
Indiana University gastroenterologist Douglas Rex says he's been switching older patients to fluid bowel-cleansers that don't contain sodium phosphate since the first reports of kidney problems came out in 2005. Rex serves as a scientific adviser to Salix Pharmaceuticals, maker of Visicol, OsmoPrep and MoviPrep, one of the fluid products.
No one knows how many people may have suffered damage from the sodium phosphate bowel-cleansers, because even those who've lost 75% of their kidney function feel fine, says Columbia University pathologist Glen Markowitz. Markowitz, a Salix consultant, was lead author of a 2005 report on kidney damage in 21 patients who had taken sodium phosphate bowel-cleansers. Even when detected, he says, a connection to the products could be missed.
Dallas gastroenterologist Lawrence Schiller says a patient who had an easy time with the pills wasn't thrilled to learn of the kidney issue. Schiller left future choice of prep up to her, noting: "There's a one-in-a-million chance you could end up on dialysis with (the pills)."