RESULTS OF LONG-TERM TREATMENT WITH ORTHOPHOSPHATE AND PYRIDOXINE IN PATIENTS WITH PRIMARY HYPEROXALURIA

Background. The prognosis for patients with primary hyperoxaluria has been ominous, with the expectation of renal failure, poor results with transplantation, and early death. Methods. We studied the long-term e ffects of orthophosphate and pyridoxine therapy in 25 patients with pr imary hyperoxaluria who were treated for an average of 10 years (range , 0.3 to 26). Their mean age at the start of treatment was 12 years (m edian, 6; range, 0.5 to 32). We also studied the effect of orthophosph ate and pyridoxine on urinary supersaturation with calcium oxalate, cr ystal inhibition using a seeded growth system, and crystal formation u sing scanning electron microscopy in 12 patients during three-day stay s in the clinical research center. Results. The mean (+/-SD) glomerula r filtration rate at the start of treatment was 91+/-26 ml per minute per 1.73 m(2). The median decline in glomerular filtration rates was 1 .4 ml per minute per 1.73 m(2) of body-surface area per year. The actu arial survival free of end-stage renal disease was 96, 89, 74, and 74 percent at 5, 10, 15, and 20 years, respectively. Treatment with ortho phosphate and pyridoxine reduced urinary supersaturation with calcium oxalate from 8.3+/-3.0 to 2.1+/-1.7 kJ per mole at 38 degrees C (P<0.0 01), increased the inhibition of calcium oxalate formation from 63+/-1 1 to 108+/-10 inhibitor units per 24 hours (P<0.001), and improved the crystalluria score from 2.6+/-0.3 to 0.6+/-0.1 (P<0.001). Conclusions . Treatment of patients with primary hyperoxaluria with orthophosphate and pyridoxine decreases urinary calcium oxalate crystallization and appears to preserve renal function.