RESPONSE

Abstract

To the Editor: We appreciate the comments from Dr. Parmar regarding his concern over the use of urine alkalinization [e.g., tricitrates (oral Polycitra)] for patients receiving combination therapy with both the ketogenic diet and carbonic anhydrase inhibitors. Although theoretically the acidification of the diet and alkalinization of carbonic anhydrase inhibitors could counteract each other, they do not seem to do so clinically. Should this have been the case, one would have expected a decreased risk, lower than even the 2–4% reported for topiramate or zonisamide alone. As mentioned in our study, we found an almost identical risk of kidney stones with this combination to that with the use of the ketogenic diet alone. We therefore suspect that the acidification properties of the diet are the predominant influence on kidney stone formation. For years, oral polycitrates have been very beneficial in our ketogenic diet patients when this occurs. We acknowledge the lack of data to prove the benefit of polycitrates for combination therapy patients. We hope this will improve. We agree with Dr. Parmar against routinely recommending polycitrate use, because a lack of risk without evidence of gain is not a valid reason to start a daily medication. In our discussion, however, we did not recommend its use for these patients routinely, but only for those with higher risk for stones (either a family history of kidney stones or prior urologic abnormalities). In these patients, we strongly support the prophylactic use of oral polycitrates when combination therapy is started.