Lawsuits began last month for four people who say the prescription bowel cleanser OsmoPrep caused them kidney damage that resulted in dialysis. OsmoPrep, made by Salix Pharmaceuticals, is a type of laxative called oral sodium phosphate, or OSP, used to cleanse the intestines prior to procedures such as colonoscopy. Salix Pharmaceuticals began marketing OsmoPrep in 2006. The drug generated more than $30 million in sales in 2008.
In December 2008, the Food and Drug Administration (FDA) issued a black box warning on OSP products, specifically Salix’s OsmoPrep and its similar drug Visicol, after receiving numerous reports of a serious kidney injury occurring after use of the products. The injury is known as acute phosphate nephropathy. Those most at risk of developing the serious kidney injury are the elderly and those with preexisting kidney problems, however some people with no risk factors have fallen ill from OSPs. An FDA black box warning is the most serious warning the FDA can issue and is placed on products that carry a risk of severe adverse events or death.
Following the FDA warning, over-the-counter OSP solutions such as Fleet Phospho-Soda made by C.B. Fleet, were pulled from store shelves. While the FDA says the products are safe when used in lower doses as a laxative, in higher doses the solutions posed the same risk as the prescription OSP products.