To the Editor.—
Dr. Berman's article suggests the use of the carbonic anhydrase inhibitor acetazolamide (Diamox) to improve the effectiveness of orally given sodium bicarbonate in alkalinization of the urine for prevention of uric acid and cystine calculi. Acetazolamide reduces citrate excretion, thereby increasing the risk of calcium-containing stone formation. A safer alternative is one of the thiazide natriuretic drugs such as chlorothiazide or hydrochlorothiazide. These drugs, in addition to increasing sodium excretion, thereby alkalinizing the urine, decrease urinary calcium excretion, thus preventing the formation of a calcium stone. It seems of little benefit to prevent a uric acid stone only to foster growth of a calcium-containing stone.