Magazine article Drug Topics

FDA Approves Ferric Citrate to Treat Hyperphosphatemia in Dialysis Patients

Magazine article Drug Topics

FDA Approves Ferric Citrate to Treat Hyperphosphatemia in Dialysis Patients

Article excerpt

NEW DRUG REVIEW Steven M. Lemieux, PharmD; Kevin W. Chamberlin, PharmD

Ferric citrate (Auryxia; Keryx Biopharmaceuticals) is an iron-based phosphate binder. FDA approved it September 5, 2014, for the treatment of hyperphosphatemia in chronic kidney disease (CKD) patients on dialysis.

Overview

In CKD, progressive inability of the kidneys to eliminate phosphorus can result in hyperphosphatemia. First-line treatment is restriction of dietary phosphorus. When this is insufficient to maintain serum phosphorus within normal limits, treatment with a phosphate binder begins. As a class, these medications consist of cations that, when taken with meals, bind anionic dietary phosphorus, forming insoluble complexes that are then excreted, limiting phosphate absorption.

Efficacy

Ferric citrate's capacity to lower serum phosphorus in CKD patients on dialysis has been examined in two clinical trials. In both instances, ferric citrate use was associated with decreased serum phosphorus levels throughout the study duration.

Study 1 was a 56-week trial consisting of a 52-week active-controlled phase in which ferric citrate was compared to calcium acetate and sevelamer carbonate, followed by a four-week placebo-controlled, randomized withdrawal period.

Before randomization, patients underwent a two-week washout period, during which phosphate binder administration was prohibited. Patients randomized to ferric citrate use began treatment with a dose of 6 g per day; those randomized to use of calcium acetate or sevelamer carbonate resumed their maintenance dose prior to the washout period. The dose of all phosphate binders was titrated up to a maximum of 12 tablets per day to achieve serum phosphorus levels between 3.5 mg/dL and 5.5 mg/dL.

Ferric citrate use led to decreases in serum phosphorus comparable to those of the active control group throughout the 52-week treatment duration. Ferric citrate-treated patients were then randomized either to continue treatment or to receive placebo during the four-week withdrawal period.

At its end, those on placebo experienced an increase in serum phosphorus by 2.2 mg/dL compared to patients using ferric citrate, an effect that achieved statistical significance (P<0.0001).

The second efficacy study was a fixed-dose, open-label trial in which 154 hyperphosphatemic CKD patients on dialysis underwent a one- to two-week washout period and were then randomized to receive 1 g, 6 g, or 8 g of ferric citrate per day for four weeks. …

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