Clinical results of allopurinol treatment in prevention of calcium oxalate stone formation.

Allopurinol in a daily dose of 300 mg. was administered to 99 patients with calcium oxalate stone disease. Treatment was started irrespective of urine composition and was continued for up to 8 years. Only 43 per cent of the patients treated for 5 or more years remained free of further stone formation, a result not better than observations in untreated stone patients. When patients were subgrouped with respect to recurrent or nonrecurrent stone formation during treatment, the former group, besides being followed for longer intervals than the latter group, had a urine composition suggesting a higher crystallization risk. We concluded that with the possible exception of hyperuricosuria or hyperuricemia the indication for allopurinol treatment of recurrent calcium oxalate stone disease is weak. The results also demonstrate clearly the problems combined with evaluation of prophylactic medical therapy in patients with calcium stones. The necessity of long-term followup and analysis of the biochemical risk situation is emphasized.