Treating C. difficile

We agree with Malvinder Parmar that the role of anion-binding resins in the treatment of CDAD needs to be studied further. Anion-binding resins, such as cholestyramine and colestipol, have been shown to bind C. difficile toxins¹ and have consequently been proposed as potentially useful in the treatment of CDAD, as we mentioned in our review.² Parmar also suggests that anion-binding resins may also bind C. difficile spores, but to the best of our knowledge, this phenomenon has not been described in published reports. Small numbers of mostly anecdotal reports of success and failure with the use of anion-binding resins in the treatment of CDAD have been published (summarized by Ariano and associates³), but no large randomized controlled trials have been completed to definitively determine the role of resins. Anion-binding resins have been shown to bind vancomycin^1,4 and theoretically may bind other antibiotics such as metronidazole, although we are not aware of any published data specifically describing this. Given the possibility of antibiotic binding by resins, some authors have suggested not using anion-binding resins in the treatment of CDAD,⁵ whereas others recommend using them only if administered at different times from metronidazole or vancomycin.⁶ As Parmar suggests, more study is needed to address the optimal indication and timing of anion-binding resins in the treatment of CDAD.

Susan M. Poutanen Andrew E. Simor Department of Laboratory Medicine and Pathobiology University of Toronto Toronto, Ont.