Black Box Warning added on Visicol and OsmoPrep for Effects on Kidneys

Before having a colonoscopy, patients have to go through the process of flushing out their bowels. However, new information indicating that this may be the most dangerous part of the procedure, as the drugs products that assist in the flushing may pose a risk of acute kidney injury.

The Food and Drug Administration has mandated Salix Pharmaceuticals Ltd., the manufacturer of two of the most commonly used prescription flushing products, Visicol and OsmoPrep, to put a “black box” warning on its labels. A “black box” warning is the most severe warning that the FDA issues on prescription medications. The agency further directed the drug manufacturer to conduct a clinical trial to specifically assess the risk of the products, especially to the kidneys.

The most vulnerable populations of patients to such effects on the kidneys are those older than 55; those who already suffer from dehydration, kidney disease, acute colitis or delayed bowel emptying; and those people taking other medicines that affect kidney function.

Dehydrated patients taking such medication have always been a concern, which is why even the current label suggests drinking a half-gallon of water when ingesting the drugs. Dehydration already affects kidney functions, so the combination of dehydration and these medications can be extremely dangerous.

The FDA also indicated that similar over-the-counter products, such as Fleet Phospho-soda, could have the same risks. Patients should only take such OTC medications in consultation with their physicians, and in fact, the FDA cautions consumers against using OTC cleansing products at all until further research is completed.

If you or a loved one were taking Visicol, OsmoPrep, or a similar drug and have since been diagnosed with kidney problems, please contact our office via our website at for a free consultation so that we can work with you to protect your rights.