On the basis of almost 15 years of experience with
thiazide treatment in 346 patients with
calcium stones, we believe that the following conclusions are justified: 1) Stone progression ceases in at least 90% of patients who take
hydrochlorothiazide (50 mg, twice daily) on a regular basis. 2) A reduced dose of
hydrochlorothiazide, i.
e., 25 mg twice daily, appears to be effective in a significant proportion of patients. 3)
Thiazides are effective in normocalciuric as well as hypercalciuric patients and in most patients with tubular
ectasia (
medullary sponge kidney). 4. Side effects necessitate discontinuation of
thiazide treatment in approximately 7% of patients. The incidence and severity of side effects is reduced by initiating treatment with a small dose and by increasing the dose progressively until the full maintenance dose is achieved. A trial with a reduced dose is warranted in patients who are unable to tolerate the regular maintenance dose. 5) The therapeutic efficacy of
thiazides in stone prevention cannot be accurately predicted by the degree of hypocalciuric response. Stone prevention may cease despite a minimal hypocalciuric response, whereas stone progression may occur when an adequate hypocalciuric response has taken place. 6) In addition to the hypocalciuric action,
thiazides reduce urine
oxalate excretion and increase urine
zinc and (probably)
magnesium; these effects probably contribute to the efficacy of this agent in stone prevention.