Clinical effect of captopril on the formation and growth of cystine calculi.

We determined the clinical efficacy of captopril for the prevention of new or stone growth in patients with homozygous cystinuria. Nine patients with a history of multiple cystine stones despite standard fluid and alkalization therapy received 50 mg. captopril, 3 times daily in addition to the standard therapy. Before treatment the rate of new stone formation or stone growth ranged from 0.7 to 2.0 events (mean 1.2) per patient-year for 1 to 3 years of observation (mean 1.9). During treatment the rate ranged from 0 to 3.0 events (mean 1.03) per patient-year for 0.5 to 6 years (mean 2.9). Although statistical significance was not evident for the group as a whole (p = 0.35), our findings suggest that captopril may be clinically efficacious in at least some patients with difficult to control cystinuria. Recommendations regarding its indications in this setting are made.