 5. Subjects receiving pyridoxine must be receiving a stable dose for at least 3 months prior to entry in to the study and must remain on the stable dose during the study. Other non-pyridoxine naïve subjects e.g. Pyridoxine non-responder: 30 reduction of the urine oxalate levels not receiving pyridoxine at study entry must be willing to refrain from initiating pyridoxine during study participation. Note: There will be no pyridoxine-naïve subjects enrolled in the study. 