Metabolic effects of thiazide versus placebo in patients under long-term treatment for recurrent urolithiasis

Thiazide induced metabolic effects reflected in serum and 24 h urine excretions were investigated in general practice in 48 recurrent urinary calcium stone formers on prophylaxis with 50 mg hydrochlorthiazide or placebo (average duration of treatment 3 years). After 10 months of treatment, there was a significantly greater decrease in urinary calcium excretion among patients receiving thiazide than in patients given placebo (p less than 0.05). There was a significant increase in urinary magnesium in the thiazide group (p = 0.02), while there was no significant alteration in urinary uric acid. An increase was observed in the 24 h urine volume of 400 ml in the placebo group in contrast to a decrease in the thiazide group. The effects on serum calcium, potassium and uric acid were in accordance with previous reports. Few and only mild side effects were observed except for one attack of gout. The necessity of having adequate control groups in such studies is emphasized.