Hyperphosphataemia and treatment with sevelamer in haemodialysis patients

More than 60% of patients on chronic haemodialysis (HD) have a serum phosphate level above 5.5mg/dl (1.75mmol/l), which recently has been recommended as an appropriate target in patients with end-stage renal disease (ESRD). Preventing hyperphosphataemia and elevated Ca x P product not only ameliorates the progression of secondary hyperparathyroidism and bone disease, but also appears to reduce cardiovascular morbidity and mortality from vascular calcifications. Dietary phosphate restriction and the administration of aluminium and calcium salts have been the principal means of phosphate control over the last decade. Unfortunately, the protean disturbances of toxic aluminium accumulation in the body virtually eliminated aluminium from clinical practice. Calcium-based therapy, although well tolerated, results in frequent hypercalcaemia when administered concurrently with vitamin D analogues, despite a decrease in the concentration of dialysate calcium. Sevelamer (Renagel(R)) has been a novel, non-absorbable calcium- and aluminium-free synthetic polymer. In initial studies, sevelamer reduced serum phosphate, Ca x P product and parathyroid hormone (PTH) in a manner comparable with calcium acetate therapy. However, the effect on PTH levels may prove to be inconsistent. It seems somewhat less effective in binding phosphate than aluminium, although no direct comparisons have been made. In a recent study, it attenuated the progression of vascular calcification in HD patients. It also binds bile acids, resulting in substantially lower low-density lipo-protein cholesterol levels. The major obstacle to its current use is a substantial increase in the cost associated with sevelamer therapy.