Phosphate Binders

Several retrospective studies of large databases have shown that most dialysis patients have elevated levels of serum phosphorus and that this elevation, independent of a variety of relevant variables, adversely affects patient survival (1,2). Although there are no data demonstrating that a reduction of serum phosphorus will improve survival, a prudent clinician cannot dismiss this compelling epidemiologic evidence and will strive to lower serum phosphorus in dialysis patients. Although the Kidney Disease Outcomes Quality Initiative guidelines indicate that a serum phosphorus value that exceeds the upper limit of normal is acceptable for dialysis patients (3), more recent data suggest that we should aim for a level of phosphorus within the normal laboratory range (4).Phosphorus is ubiquitous in our daily diet, and its absorption is poorly regulated. We continue to absorb approximately 60 to 70% of dietary phosphorus regardless of bodily needs or renal function (5). As our renal excretory capacity diminishes, unrelenting absorption coupled with impaired excretion results in phosphorus retention. Dialysis effectively removes a single day’s worth of absorbed phosphorus (6); our patients generally receive dialysis only 3 d/wk, but they continue to eat on all 7 days. Therefore, to prevent phosphorus retention, we must first decrease dietary phosphorus, which results in less absorption and is always worthwhile but limited by …