RENAL4: Indoxyl Sulfate Removal by NORIT RO Carbon and the Adsorba 300 Hemoperfusion Column

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Purpose: Indoxyl sulfate is a protein-bound uremic toxin typically cleared by the kidneys. In end-stage renal disease (ESRD) it accumulates, contributing to vascular disease and possible early mortality. A number of novel charcoal-based adsorbents remove indoxyl sulfate, but the FDA-approved Adsorba 300 column has never been tested for this. Indoxyl sulfate removal using a currently approved medical device would be of great practical value. Methods: We studied indoxyl sulfate removal from albumin solutions. We first used a charcoal column designed in our lab and a commercially available Norit RO 0.8 based charcoal. Norit RO 0.8 resembles the charcoal in the Adsorba 300. We tested bovine and human serum albumin solutions (BSA and HSA respectively). Indoxyl sulfate was measured by mass spectrometry. After this proof of concept, we used Adsorba 300 columns. Results: We found that adsorbent columns made with Norit RO 0.8 can remove indoxyl sulfate from BSA and HSA solutions. With the Adsorba 300 column indoxyl sulfate concentration fell below the limit of detection within 15 minutes from a BSA solution. Summary: The clinically available Adsorba 300 hemoperfusion column can remove the albumin bound uremic toxin indoxyl sulfate in vitro. This toxin is not dialyzable. This detoxification option may improve treatment of ESRD. In vivo testing should be considered.