The story of Kayexalate!

Hyperkalemia is a life-threatening emergency that can cause arrhythmias and cardiovascular collapse. As Emergency Physicians, we must be able to anticipate and treat Hyperkalemia better than anyone else. No surprise, why we have been about the management of Hyperkalemia “n” number of times. Lets look at the evidence behind one of the treatment modalities for Hyperkalemia;  “Kayexylate” aka “K-Bind/SPS”.

Sodium polystyrene sulfonate (SPS, Kayexalate) is a cation-exchange resin that has a higher affinity for potassium than sodium. In the lumen of the colon, it exchanges sodium for secreted potassium. It can cause severe constipation; therefore sorbitol/mannitol is added to it as a cathartic. FDA approved K Bind in 1958. This was based in two studies done with very limited number of patients were published in NEJM, 1961 supported the use of SPS. There were potential flaws with these studies like no control group; patients were fed with sugar (which causes insulin release and decreases potassium) and poor statistical analysis.

1. Scherr et al. 32 patients with hyperkalemia and renal failure, various doses of SPS were given with various dosing schedules and courses of treatment. Reduction of serum K by 0.4 in 66% pts after 24 hours. Not a RCT, no controls, patients in the study were also on: low potassium diets, many received bicarb/insulin/glucose

2. Flinn et al, 10 patients, 5 kayexalate/sorbitol PO, 3 sorbitol, 2 kayexalate/sorbitol enema. All on low potassium diets and diuretics. 5 days QID dosing, steady decrease in potassium.

In addition to the questionable benefit, now there is mounting evidence describing constipation and colonic necrosis with the use of SPS. In 2011, FDA issued a warning with the use of SPS. There is more and more literature coming up against the use of SPS. Evidence Based Medicine has come a long way over last 50 years and we need to review this practice.

So, SPS is a potentially harmful therapy to treat hyperkalemia, it has a slow onset action (if at all) and  doubtful efficacy. It also carries risk of life threatening gastrointestinal complications. There is no convincing evidence that SPS increases fecal potassium losses.

So next time, ask yourself if SPS (K-Bind) is really required !

References:

1.  Sterns RH, Rojas M, Bernstein P, Chennupati S. Ion-exchange resins for the treatment of hyperkalemia: Are they safe and effective? J Am Soc Nephrol 21: 733-5, 2010

2.   Gruy-Kapral C, Emmett M, Santa Ana CA, et al. Effect of single dose resin-cathartic therapy on serum potassium concentration in patients with end-stage renal disease. J Am Soc Nephrol 9: 1924–30, 1998.

3.  Bomback A, Woosley JT, Kshirsagar AV. Colonic necrosis due to sodium polystyrene sulfate (kayexalate). Am J of EM 27: 753.e1-753.e2, 2009.

4.   Welsberg LS. Management of severe hyperkalemia. Crit Care Med 36: 3246-51, 2008.

5.  Rogers BR, LI SC. Acute colonic necrosis associated with sodium polystyrene sulfonate (kayexalate) enemas in a critically ill patient: Case report and review of the literature. J Trauma 51: 395-7, 2001.

6. Systematic review of adverse events caused by kayexalate (The American Journal of Medicine Volume 126, Issue 3 , Pages 264.e9-264.e24, March 2013)

7.  http://www.accessdata.fda.gov/drugsatfda_docs/label/2011/011287s023lbl.pdf