Prevention of Recurrent Nephrolithiasis in Adults

IN RESPONSE:

Dr. Bell raises an important issue and suggests that the American College of Physicians should offer guidance on what drugs to use under specific circumstances. We acknowledge in the guideline that biochemistry suggests a link between the mode of action of the various drugs and stone type. However, results were mixed about whether baseline biochemistry measures predicted treatment effectiveness for reducing the risk for stone recurrence or for the efficacy of dietary or pharmacologic treatments compared with placebo or controls for recurrent stone outcomes. In addition, no randomized, controlled trials compared risk for stone recurrence according to follow-up biochemistry measures or changes from pretreatment biochemistry values. A post hoc analysis of 1 randomized, controlled trial described in the evidence review on which this guideline was based (1) suggested that the benefit of allopurinol treatment was limited to patients with baseline hyperuricemia or hyperuricosuria. However, this finding was the only available evidence from a randomized, controlled trial linking stone biochemistry to recurrent stone outcomes, it was only for 1 drug, and the analysis was done post hoc. As we point out in the guideline, we are aware that many physicians do select medications on the basis of stone type (for example, allopurinol for uric acid stones) and we do not discourage that practice.