Effect of pyridoxine supplementation on plasma oxalate concentrations in patients receiving dialysis

Plasma oxalate and erythrocyte glutamic oxaloacetate transaminase activity (EGOT) (an indicator of nutritional status with respect to pyridoxine) were measured in 21 patients maintained on regular continuous ambulatory peritoneal dialysis or haemodialysis before and after a 4-month period of supplementation with pyridoxine, 100 mg day-1. Prior to supplementation 10/21 patients showed subnormal EGOT activity, although the increment in activity on addition of pyridoxal-5-phosphate in vitro was within the normal range in all cases. Mean plasma oxalate was 31.5 μmol 1-1 (SEM 2.9) prior to supplementation and did not change significantly with supplementation, despite normalization of EGOT activity in all but 2/21 patients. We conclude that pyridoxine deficiency does not contribute significantly to hyperoxalaemia in patients receiving dialysis and that 100 mg of pyridoxine daily is insufficient to reduce oxalate generation by a pharmacological action on glycine transamination.