Several patients who say they suffered kidney damage after taking OsmoPrep are suing Salix Pharmaceuticals, the maker of the popular oral sodium phosphate (OSP) tablets used as a bowel cleanser before colonoscopies. In many cases the gastroenterologist and the endoscopy center are also named as defendents.

Ten lawsuits have been filed against Salix Pharmaceuticals, and none have been decided by a judge or jury yet, says Charles Hurd, an attorney with the Houston law firm of Fulbright & Jawarski, which is representing Salix in the lawsuits. Mr. Hurd wouldn't comment on the specifics of the cases since they are pending litigation. "OsmoPrep is safe and effective when used as directed," he said in an e-mail. In court documents filed this month the company denies any allegations of negligence.

Many of the lawsuits have been filed by patients who took OsmoPrep before December 2008, when the FDA began requiring a black box warning on the packages of the prescription-only OsmoPrep and Visicol products sold by Salix, based in Morrisville, N.C.

The black box warns of greater risk for patients with "increased age," hypovolemia, bowel obstruction, active colitis, kidney disease, and patients taking diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and in some cases, NSAIDs.

In a suit filed in U.S. District Court for the Northern Mississippi Delta, Christine Buxton, of Southhaven, Miss., claims that she suffered kidney damage in 2007 after taking OsmoPrep before a routine colonoscopy. "Her kidneys totally shut down, and she's been on dialysis," says her attorney, Zach Butterworth, of the Hesse & Butterworth law firm in Bay St. Louis, Miss.

The lawsuit filed in June 2009 claims that that Salix, Ms. Buxton's gastroenterologist, Eric Ormseth, MD, and the Gastroenterology Center of the Midsouth, in Germantown, Tenn., knew about the danger that OsmoPrep posed. "It was pretty well-known in the medical community," says Mr. Butterworth.

In court documents, Dr. Ormseth and the endoscopy center deny their negligence and claim that Ms. Butxon received care above the standard of care. The attorney for Dr. Ormseth and the endoscopy center declined to comment on the case.

OSP has been associated with acute kidney injury since 2005. After a study published in April 2008, researchers at Texas A&M University suggested that its use should be discouraged in elderly patients. Between 2006 and mid-December 2008, the FDA received 20 reports of kidney damage associated with OsmoPrep.

"We cannot rule out, however, that some of these patients were dehydrated prior to ingestion of OSP products or they did not drink sufficient fluids after ingesting OSP products," said Janet Woodcock, MD, director of the FDA's Center for Drug Evaluation and Research, in a 2008 statement regarding OsmoPrep's black box warning.

The lawsuits could be a class action suit in the making. Litigation will be going on "for years," says Paul Rheingold, an attorney from the firm Rheingold, Valet, Rheingold, Shkolnik & McCartney in New York, which is representing 4 plaintiffs in North Carolina who took OsmoPrep before the black box warning was required. "This is just ramping up."

Kent Steinriede