LAUSR

Patients on maintenance hemodialysis (HD) generally require management of hyperphosphatemia and take phosphate binders (PBs) such as ferric citrate (FC) and lanthanum carbonate (LC) [1]. Meanwhile, many HD patients require antacid therapy (AAT). Although PBs have been administered regardless of AAT, a recent clinical analysis revealed that concomitant AAT hindered the phosphatebinding efficacy (PBE) of LC [2]. Here, we describe our experience with FC-for-LC substitution under AAT and suggest that the PBE of PBs in clinical practice differs from that expected from experimental studies. We selected HD patients (age ≥ 18 years, 4–5 h/session, 3 times/week) receiving AAT for whom a 250-mg FC tablet (FC250) was substituted for a 250-mg LC tablet (LC250) to improve iron stores [3] and whose other medications were unchanged in the 6 weeks before and after the substitution. Statistical analyses were performed using SPSS Statistics software (IBM Corp., Armonk, NY, USA). Among 10 eligible patients, normalized protein catabolism rate (nPCR) did not change following the substitution, with mean (standard deviation) nPCR values of 1.12 (0.18) and 1.14 (0.23) g/kg/day (p = 0.70) before and after the substitution, respectively. The substitution reduced serum inorganic phosphate concentration ([iP]) significantly (Fig. 1) and serum intact parathyroid hormone concentration (iPTH) generally; the mean (standard deviation) values of [iP] were 6.0 (0.7) and 4.9 (1.0) mg/dL (p < 0.001) and those of iPTH were 190 (61) and 185 (58) pg/mL (p = 0.85) before and after the substitution, respectively. The decrease in [iP] indicates PBE was better with FC250 than with LC250 in our HD patients receiving AAT, which increased the pH of their gastric fluid. This is in contrast to the experimental findings [4, 5]. In these studies, FC, which provided PBE as potent as LC did at the same doses in solution with pH 2, lost PBE in solution with pH greater than 3, while the PBE of LC decreased only gradually when the solution pH was increased from 2 to 8. Since FC250 contained 250 mg FC and LC250 contained 477 mg LC, the studies suggested that FC250 could provide at most around half the PBE of LC250. Thus, the practical PBE of FC250 and LC250 appeared to differ from that expected from the experimental studies. We did not examine substitution of LC for FC, and any change in dietary phosphate intake, the primary determinant of [iP], could have influenced our findings [1], although nPCR, which would reflect dietary intake, did not change significantly following the substitution. Furthermore, the findings of this retrospective analysis with a small sample size at a single center were limited by possible selection bias. Thus, the PBE of PBs in clinical practice should be examined in future studies that are larger in scale and examine the influence of concomitant therapy.