Urinary oxalate levels are not affected by dietary purine intake or allopurinol

We showed previously that ingestion of a non-specific high purine diet by healthy subjects increased not only urinary uric acid levels but urinary oxalate as well. Both increments were reduced significantly during concomitant allopurinol therapy. The present study was undertaken to investigate these findings in more detail under carefully controlled dietary conditions where a single specific purine, guanosine, was used as an additive and several different methods for oxalate determination (GLC, HPLC, isotacophoresis) were compared with the enzymatic method used previously. Results obtained by two direct techniques of oxalate determination showed no significant alteration in oxalate levels during any dietary regime, suggesting that the earlier results derived from problems inherent in the experimental design and methodology employed. The study confirmed that one of the beneficial effects of allopurinol was to reduce dietary purine absorption. The results may thus provide a logical explanation for the reduced incidence of urolithiasis during allopurinol therapy in some idiopathic oxalate stone formers addicted to purine-rich foods and beverages.