Long-term studies show that citrate therapy effectively reduces the frequency of new stone formation. Therapy with an equivalent amount of sodium bicarbonate may achieve the same hypocitraturic effect but is generally not well tolerated because of gastric bloating or belching. Moreover, increased intake of sodium may adversely affect response to therapy by increasing urinary calcium excretion. It has been suggested that concurrent hypercalciuria and hyperuricosuria may underlie a particularly virulent form of recurrent nephrolithiasis. The treatment of hyperuricosuria with dietary purine restriction or with allopurinol may be beneficial in these patients if the usual treatment of hypercalciuria fails to alleviate the disorder.
Ion exchange resins such as cholestyramine can also reduce oxalate absorption.
Cholestyramine may be administered in a dosage of 4 g two to four times a day. This resin binds bile acid, the free form of which increases colonic absorption of oxalate by increasing its permeability across the intestinal wall. Cholestyramine may also bind oxalate in the intestinal lumen. A trial of pyridoxine is indicated in those cases in which the dietary restriction of oxalate and increase of calcium intake are not effective in reducing hyperoxaluria. In those patients with increased excretion of uric acid, treatment options include dietary purine restriction, urinary alkalinization, and the administration of allopurinol.