DIPYRIDAMOLE DECREASES RENAL PHOSPHATE LEAK AND AUGMENTS SERUM PHOSPHORUS IN PATIENTS WITH LOW RENAL PHOSPHATE THRESHOLD

It has been shown that an acute infusion of dipyridamole increased ren al phosphate reabsorption in rats and humans. A prospective study was performed to determine whether chronic treatment by dipyridamole given orally could decrease renal phosphate leak and increase serum phospho rus in patients with idiopathic low renal phosphate threshold (TmPO4/G FR < 0.77 mM). Sixty-four patients with low TmPO4/GFR were included an d treated with dipyridamole (75 mg, 4 times daily) for more than 12 mo . Serum phosphorus, TmPO4/GFR, parathyroid hormone, serum calcium, and 1,25-dihydroxyvitamin D were measured sequentially before treatment, and after 3, 6 to 9, and 12 mo of treatment. Under chronic treatment w ith dipyridamole, TmPO4/GFR and serum phosphorus significantly increas ed in 80% of patients within 3 mo, with maximal values reached within 9 mo. This improvement persisted after 12 mo of treatment. In 28 patie nts, 1,25-dihydroxyvitamin D concentrations were above the normal rang e (>42 pg/ml) and normalized in parallel with the increase of serum ph osphorus. The 24-h calcium excretion (which was initially increased in patients with high vitamin D concentrations) and urolithiasis decreas ed under treatment. Ionized serum calcium and parathyroid hormone rema ined unchanged. After 2 yr, treatment was discontinued in three patien ts; serum phosphorus and TmPO4/GFR decreased within 1 mo after discont inuation. Dipyridamole at a dose of 75 mg 4 times daily increases low TmPO4/GFR and improves hypophosphatemia in patients with renal phospha te losses and can be used to treat these patients.