Ion-Exchange Resins for the Treatment of Hyperkalemia: Are They Safe and Effective?
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CLINICAL COMMENTARY www.jasn.org Ion-Exchange Resins for the Treatment of Hyperkalemia: Are They Safe and Effective? Richard H. Sterns, Maria Rojas, Paul Bernstein, and Sreedevi Chennupati Rochester General Hospital and University of Rochester School of Medicine and Dentistry, Rochester, New York ABSTRACT Sodium polystyrene sulfonate (SPS), an ion-exchange resin designed to bind po- the FDA were to consider SPS in sorbitol tassium in the colon, was approved in 1958 as a treatment for hyperkalemia by the and Kayexalate powder as new therapeu- US Food and Drug Administration, 4 years before drug manufacturers were re- tic agents today, would they be approved quired to prove the effectiveness and safety of their drugs. In September 2009, as safe and effective? citing reports of colonic necrosis, the Food and Drug Administration issued a Synthetic cation-exchange resins, warning advising against concomitant administration of sorbitol, an osmotic ca- which became available to industry in thartic used to prevent SPS-induced fecal impaction and to speed delivery of resin 1935, are insoluble polymers with a mo- to the colon, with the powdered resin; however, a premixed suspension of SPS in lecular structure resembling a crystal lat- sorbitol, the only preparation stocked by many hospital pharmacies, is prescribed tice to which reactive carboxylic or sul- routinely for treatment of hyperkalemia. We can find no convincing evidence that fonic groups are attached. When a resin SPS increases fecal potassium losses in experimental animals or humans and no is placed in a solvent, the resin’s reactive evidence that adding sorbitol to the resin increases its effectiveness as a treatment groups, which may be preloaded to form for hyperkalemia. There is growing concern, however, that suspensions of SPS in sodium, potassium, calcium, ammo- sorbitol can be harmful. It would be wise to exhaust other alternatives for manag- nium salts, or combinations of these ing hyperkalemia before turning to these largely unproven and potentially harmful ions, exchange their bound cations with therapies. cations dissolved in the solvent.3 Medical applications of synthetic res- J Am Soc Nephrol 21: 733–735, 2010. doi: 10.1681/ASN.2010010079 ins were first explored in 1946.3 At ap- proximately the same time, clinical mea- surements of serum potassium became Kayexalate (sodium polystyrene sulfo- widely. A 6-month single-center survey available and the clinical consequences nate [SPS]), an ion-exchange resin de- from an emergency department reported of “potassium intoxication” were first signed to exchange sodium for potas- 1001 patients who received SPS in sorbi- recognized.4 In an era when hemodialy- sium in the colon, is approved for use in tol for hyperkalemia and only 188 pa- sis was not easily available, the newly ac- the treatment of hyperkalemia. In Sep- tients who received other potassium- cessible resins were embraced as a possi- tember 2009, the US Food and Drug Ad- lowering therapies.2 An unpublished ble treatment for hyperkalemia. ministration (FDA) posted safety label- hospital-wide survey of inpatient prac- Studies of dogs showed that a carbox- ing changes for Kayexalate powder on its tice patterns at our own hospital yielded ylic acid exchange resin in the hydrogen web site. The warning reads, “Cases of similar results with 1800 doses of SPS in cycle causes metabolic acidosis with a colonic necrosis and other serious gas- sorbitol given in the past year, a 30% in- large increase in fecal sodium and potas- trointestinal adverse events (bleeding, crease from a survey 2 years earlier. sium and a reciprocal decrease in urinary ischemic colitis, perforation) have been Does SPS in sorbitol deserve its cur- reported in association with Kayexalate rent popularity? Do benefits from the use. The majority of these cases reported drug outweigh its risks? The FDA first Published online ahead of print. Publication date the concomitant use of sorbitol.. Con- approved Kayexalate for the treatment of available at www.jasn.org. comitant administration of sorbitol is hyperkalemia on June 5, 1958, 4 years be- Correspondence: Dr. Richard H. Sterns, Rochester 1 General Hospital, 1425 Portland Avenue, Rochester, not recommended.” fore passage of the Kefauver-Harris Drug NY 14621. Phone: 585-922-4242; Fax: 585-922- Despite this, prepackaged suspen- Amendments, which require drug man- 4440; E-mail: [email protected] sions of SPS in sorbitol, an osmotic laxa- ufacturers to prove the effectiveness of Copyright ᮊ 2010 by the American Society of tive, are still on the market and used their products before marketing them. If Nephrology J Am Soc Nephrol 21: 733–735, 2010 ISSN : 1046-6673/2105-733 733 CLINICAL COMMENTARY www.jasn.org cation excretion5; however, even at a drugs that were already on the market, concentration rose slightly (0.4 mEq/L) dosage of 30 to 60 g/d (equivalent to 200 ruled Kayexalate powder “effective.” on placebo and did not change during to 400 g/d in humans), a sodium-cycled Even without placebo controls, devel- the course of 12 hours in response to a resin, which exchanges sodium rather opment of hypokalemia in a patient with single dose of 30 g of resin in water, 30 g than hydrogen for potassium, caused no oliguria and hyperkalemia makes it diffi- of resin in 60 g of sorbitol, or 60 g of change in acid-base balance, little in- cult to deny that the resin is effective sorbitol alone.10 crease in fecal potassium losses, and no when taken for several days. Evidence of At the same time, evidence has grown change in urinary potassium excretion or effectiveness in the crucial first 24 hours that mixtures of resin in sorbitol may be plasma potassium concentration.5 of therapy is more tenuous. Hypokalemic harmful.11 By 2005, the FDA had re- In 1953, Evans et al.6 introduced a sul- effects of the resin cannot be distinguished ceived 35 adverse event reports of serious fonate resin charged with sodium, a pre- from the effects of the extremely-low-po- bowel injuries associated with both oral cursor of the modern resin we know as tassium diets and the concurrent adminis- and rectal administration of the mixture, Kayexalate. The investigators noted the- tration of large quantities of dextrose used many of them fatal. Extensive transmural oretical advantages of this preparation, in these studies. infarction of the colon and ileum was ob- because it avoids absorption of ammo- Soon after the introduction of Kayex- served with SPS crystals adherent to the nium, which is metabolized to urea and alate, it was recognized that the agent could mucosa and in luminal debris.11–13 The causes acidosis; however, we were unable cause severe constipation and life-threat- authors of one of the published reports to find data then or now showing that ening intestinal impactions. These obser- identified sorbitol as the culprit, because Kayexalate or its precursors increase fe- vations and the desire to speed delivery of similar bowel lesions are induced in rats cal potassium losses in experimental an- the drug to the colon led to another study with and without uremia by administer- imals. Evans et al. reported uncontrolled in 1961 of administration of resin in sorbi- ing enemas of 70% sorbitol, with or with- data showing potassium binding in the tol, a widely used over-the-counter os- out SPS, but not by giving SPS alone.11 A stool and a hypokalemic effect in four pa- motic laxative; seven patients with oliguria variety of other serious complications tients with renal failure and a single nor- were treated with three daily doses of the from SPS in sorbitol have been reported, mal volunteer.6 On the basis of necropsy resin in sorbitol, and three were given sor- including mucosal lesions in the esopha- studies of one patient who died of renal bitol alone.8 A gradual steady decrease in gus, stomach, and duodenum; fatal failure after several days of resin therapy the serum potassium over 5 days was seen chemical pneumonitis after aspiration; and another patient who died of hyper- in all cases. On the basis of limited data and rectal stenosis as a result of a foreign kalemia 18 hours after the oral adminis- without statistical analysis, the authors body reaction to SPS crystals.14–16 tration of the resin, the authors con- concluded that “sorbitol alone is as effec- Responding to concerns about ad- cluded that most potassium binding tive as a combination.” verse events, recommendations for con- occurs in the colon. This explains why For two decades, FDA-approved la- comitant or postdosing use of sorbitol the hypokalemic effect of the resin is de- beling for Kayexalate powder included were removed from FDA-approved la- layed after the first dose, reflecting the recommendations encouraging its ad- beling for the powdered resin in 2005. time required for resin to reach the co- ministration with sorbitol. In 1982, a According to a verbal communication lon, and prolonged after the last, reflect- convenient premade suspension of SPS (January 4, 2010) with the company’s ing continued delivery of orally ingested in sorbitol was approved for commercial President and its Medical Consultant, resin to the colon. distribution in the United States. A sur- Carolina Medical, the largest manufac- In 1961, Scherr et al.7 reported the vey of Drugstore and Hospital Pharma- turer of premixed suspensions, met with largest clinical experience with Kayex- ceutical purchase data in the United the FDA in 2006 and was allowed to con- alate suspended in water in an uncon- States between 1985 and 1989 showed a tinue marketing its product on the basis trolled study of patients with acute and 52% increase in the overall use of SPS of the following evidence: The Carolina chronic renal failure, using the newly ap- during this period, all of it accounted for formulation contains 33% sorbitol and proved medication provided by the by growth in the use of the prepackaged all reports of adverse gastrointestinal manufacturer, Winthrop Laboratories.