Hydrochlorothiazide compared to chlorthalidone in reduction of urinary calcium in patients with kidney stones

Abstract

Prevention of recurrent calcium stone disease includes treatment with thiazide and thiazide-type diuretics to reduce urinary calcium (UCa) levels, with the reduction in UCa correlating with risk of stone recurrence. There has been a recent trend of using lower doses of these medications and change from chlorthalidone (CTL) use to hydrochlorothiazide (HCTZ) use. It is unknown whether low doses of HCTZ are effective in lowering UCa levels to target levels. We hypothesize that HCTZ is associated with less reduction in UCa than is CTL when comparing currently used doses. Retrospective observational study of stone-formers was seen in metabolic stone clinic during a 3years period. Data included patient demographics, co-morbidities, and 24h urine electrolyte composition. Primary outcome was the change in 24h UCa. 322 patients were identified with 112 meeting criteria and used in analysis. The majority were placed on HCTZ (n=42) or CTL (n=47) 25mg QD. Patients on CTL 25mg had a greater reduction in UCa (164mg; 41%) than those on HCTZ (85mg; 21%), p=0.01. Neither CTL nor HCTZ at 12.5mg QD significantly lowered UCa. There was a decrease in serum [K] of 0.5Meq/L (p=0.001) in patients on CTL 25mg daily, but no significant difference in severe hypokalemia or arrhythmia compared to HCTZ. Our data show that CTL is associated with greater reduction in 24h UCa compared to similarly dosed HCTZ.