“The perception, mine included, was that this occurred primarily in very sick people-often in transplant patients, or following surgery, or after Kayexalate in sorbitol enemas-because that was the way that it had originally been reported. Sterns, like other nephrologists, was aware of the reports of bowel injury. I think many people assumed that even if the combination was not particularly effective for reducing potassium, it wasn’t hurting anything either.”īut over the past few years, the FDA has received several reports of serious bowel injuries, including colonic necrosis, in patients receiving SPS plus sorbitol. It became the standard operating procedure years ago, with very little data. “Sorbitol is a very convenient vehicle for suspending the SPS. Until recently, administering SPS in sorbitol was viewed as “a pretty benign treatment,” according to Michael Emmett, MD, of Baylor University Medical Center in Dallas. At many hospital pharmacies, SPS plus sorbitol is the only form of binding resin stocked. Yet for decades, the FDA-approved labeling recommended that Kayexalate be given with sorbitol. The efficacy evidence on sorbitol is even sketchier-another 1961 paper concluded that “sorbitol alone is as effective as a combination” in lowering serum potassium. Based on the Scherr report and a few others-including observations of patients who actually become hypokalemic while receiving Kayexalate-the FDA concluded that the drug was effective. remains the largest published experience with Kayexalate. The evidence included a 1961 paper by Scherr et al ( N Engl J Med 1961 264:115–119), which reported that 23 of 30 patients had at least a 0.4 mEq/L drop in plasma potassium during the first 24 hours on Kayexalate. “The Agency did go back and review Kayexalate and rule that it was effective, but it was based on what today would be considered anecdotal evidence,” said Sterns. Sterns and colleagues looked at the historical data on Kayexalate, including the FDA files. Thus Kayexalate never underwent the formal evidence review process required for drugs introduced after 1962. After the Kefauver-Harris Amendments, manufacturers had to provide scientific evidence that their products were effective as well as safe.īut drugs like Kayexalate, which had already been approved under the FD&C Act, were “grandfathered” and allowed to remain on the market-as long as their composition and labeling were unchanged. Under the 1938 Federal Food, Drug, and Cosmetic (FD&C) Act, drug manufacturers were required to demonstrate only that their products were safe. However, Kayexalate was approved in 1958-four years before passage of Kefauver-Harris Drug Amendments. “When Kayexalate is written, what’s given is a premixed preparation of the SPS resin in sorbitol.”īecause it has FDA approval, one would assume there’s adequate evidence supporting its effectiveness. “Kayelate has become synonymous with SPS-it’s kind of like Kleenex or Xerox,” said Sterns. The Kayexalate name is still widely used, even though generic preparations are most commonly given. Because of its potential to cause severe constipation, SPS is usually given with sorbitol, a widely used over-the-counter osmotic laxative. Sodium polystyrene sulfonate is an ion exchange resin designed to exchange sodium for potassium in the colon. Grandfathered drug predates modern drug approval process
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