Sodium polystyrene sulfonate (SPS), an ion-exchange resin designed to bind potassium in the colon, was approved in 1958 as a treatment for hyperkalemia by the US Food and Drug Administration. Recently, there have been cases of colonic necrosis when used in concomitant with sorbitol and especially if used in the PR form. The authors give a clinical commentary in JASN based on unpublished data at their institution and find no convincing evidence that SPS increases fecal potassium losses in experimental animals or humans and no
evidence that adding sorbitol to the resin increases its effectiveness as a treatment for hyperkalemia. There is growing concern, however, that suspensions of SPS in sorbitol can be harmful. They think its not a wise choice of drug to use for hyperkalemia.
Besides this commentary, there is one paper from 1998 that questioned this( listed below). There are two questions that arise.
1. Are resins really good and do they bind K and help in treatment of hyperkalemia?
2. Is the colonic side effect more due to sorbitol or due to the resin itself?
When first used, resin therapy was approved by FDA after few uncontrolled studies. Initially, the resins were not bound to sorbitol. Due to constipation side effects, it was started to be stocked with sorbitol. More recent data call the safety of the 33% sorbitol formulation into question. A study published in 2009 described 11 new cases of colonic necrosis associated with SPS in sorbitol, four of them fatal,
identified over 9 years in a single center. So things are now coming to question!
I think that at this point, before large studies condemn the use of resins, historic use of this drug and success in seeing that it drops the K level, its a good drug to use. This brings the entire point of evidence based medicine vs experience in question as usual again. I think that some senior nephrologists might question this theory of resins not working. I think it will be an interesting debate and lets see what comes out of it.
Any thoughts!
Other references:
http://www.ncbi.nlm.nih.gov/sites/entrez
http://www.ncbi.nlm.nih.gov/pubmed/9773794
http://www.ncbi.nlm.nih.gov/pubmed/2817643
http://www.ncbi.nlm.nih.gov/pubmed/8990142
image courtesy: rxlist.com
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