Acetazolamide is an effective adjunct for urinary alkalization in patients with uric acid and cystine stone formation recalcitrant to potassium citrate.

OBJECTIVES

Acetazolamide has been proposed as a treatment adjunct for patients with cystine and uric acid stone formation recalcitrant to standard alkalization therapy. We evaluated the effect of acetazolamide in urinary alkalization in patients with uric acid and cystine stone formation recalcitrant to potassium citrate alone.

METHODS

An institutional review board-approved, retrospective chart review identified 12 patients at 2 sites who had been prescribed acetazolamide as a treatment adjunct to potassium citrate for uric acid or cystine stones from 1997 to 2007. We evaluated the urine studies, metabolic evaluations, surgical interventions, and stone recurrence or growth.

RESULTS

The mean follow-up was 46.1 months (range 11-86). Ten patients (83%) were categorized as compliant. Of the 2 patients excluded from the study, 1 was noncompliant with the medication, and the other was lost to follow-up. Of the 10 patients who were compliant with the treatment, 5 (50%) developed adverse effects from the medication requiring discontinuation. Of the remaining 5 patients (50%) who tolerated the medication and remained compliant, 3 (60%) were stone free at a mean follow-up of 42 months. Two patients continued to form stones, including one who developed calcification of an existing uric acid stone. Both patients required surgical intervention. The mean urinary pH before treatment was 5.9 (range 5-7) and after treatment was 7.2 (range 6.5-8.5; P = .001).

CONCLUSIONS

Acetazolamide was effective in increasing the urinary pH in patients with uric acid and cystine stone formation who were already taking potassium citrate. Caution must be taken when prescribing acetazolamide, because it could be poorly tolerated and can induce calcium phosphate stone formation.