Ferric Citrate (Monograph)

Brand name: Auryxia
Drug class: Phosphate-reducing Agents
Chemical name: 2-Hydroxy-1,2,3-propanetricarboxylic acid iron (III) hydrate
Molecular formula: C₆H₅FeO₇•nH₂O
CAS number: 2338-05-8

Introduction

Phosphate binder used to reduce the intestinal absorption of phosphates.

Uses for Ferric Citrate

Hyperphosphatemia

Reduction of serum phosphorus in patients with chronic kidney disease who are undergoing dialysis.

Ferric Citrate Dosage and Administration

Administration

Oral Administration

Administer orally in divided doses with meals.

Dosage

Adults

Hyperphosphatemia

Oral

Initially, 2 g 3 times daily.

Monitor serum phosphorus concentrations and titrate dosage at intervals of 1 week or longer in decrements or increments of 1–2 g daily as needed to maintain target serum phosphorus concentrations.

Average dosage of 8–9 g daily was required to control serum phosphorus concentrations in a clinical study.

Prescribing Limits

Adults

Hyperphosphatemia

Oral

Maximum 12 g daily.

Special Populations

No special population dosage recommendations.

Cautions for Ferric Citrate

Contraindications

Iron overload syndromes (e.g., hemochromatosis).

Warnings/Precautions

Iron Overload

Iron absorption from ferric citrate may lead to excessive elevations in iron stores, especially when IV iron is used concomitantly. Elevations in serum ferritin concentrations and transferrin saturation (TSAT) observed in clinical trials.

Assess iron indices (e.g., serum ferritin and TSAT) prior to initiating ferric citrate and monitor iron indices during therapy. Patients receiving IV iron may require dosage reduction or discontinuance of IV iron.

Accidental Iron Overdosage

Accidental overdosage of iron-containing preparations is a leading cause of fatal poisoning in children <6 years of age. Keep out of reach of children. Contact a clinician or poison control center immediately in case of accidental overdosage.

GI Inflammation or Bleeding

Clinical studies did not include patients with inflammatory bowel disease or active, symptomatic GI bleeding; safety not established in these populations.

Specific Populations

Pregnancy

Category B.

Use caution. Requirements for vitamins and other nutrients are increased during pregnancy; effect of ferric citrate on absorption of vitamins and other nutrients not studied in pregnant women. Iron overdosage may carry a risk for spontaneous abortion, gestational diabetes, and fetal malformation.

Effects on labor and delivery not known.

Lactation

Iron is distributed into milk in rats; breast-fed infants may be exposed to iron from the phosphate binder when ferric citrate is administered to nursing women.

Pediatric Use

Safety and efficacy not established in children <18 years of age.

Keep out of reach of children to prevent accidental iron overdosage; iron from ferric citrate can be absorbed systemically.

Geriatric Use

No apparent differences in tolerability or efficacy relative to younger adults.

Common Adverse Effects

Diarrhea, nausea, constipation, vomiting, cough.

Drug Interactions

Effects on GI Absorption of Drugs

Possible decreased bioavailability of orally administered drugs given concomitantly; no empiric data concerning avoidance of interactions between ferric citrate and most oral drugs.

Consider administering ferric citrate and any concomitant drugs at different times if reduced bioavailability would have a clinically important effect on safety or efficacy. The spacing of doses depends on absorption characteristics of the concomitant drug (e.g., time to peak plasma concentration, formulation [i.e., immediate release or extended release]).

Consider monitoring clinical response and/or blood concentrations of concomitant drugs with a narrow therapeutic index.

Nutrients

No formal drug-food interaction studies to date. (See Actions.)

Specific Drugs

Drug	Interaction	Comments
β-Adrenergic blockers	Metoprolol, propranolol: No clinically meaningful interaction in vitro	Metoprolol, propranolol: May be administered concomitantly with ferric citrate
Amlodipine	No clinically meaningful interaction in vitro	May be administered concomitantly
Aspirin	No clinically meaningful interaction in vitro	May be administered concomitantly
Clopidogrel	No clinically meaningful interaction in vitro	May be administered concomitantly
Digoxin	No clinically meaningful interaction in vitro	May be administered concomitantly
Doxycycline	Extensive binding of doxycycline in vitro	Administer oral doxycycline at least 1 hour before ferric citrate
Enalapril	No clinically meaningful interaction in vitro	May be administered concomitantly
HMG-CoA reductase inhibitors (statins)	Atorvastatin, fluvastatin, pravastatin: No clinically meaningful interaction in vitro	Atorvastatin, fluvastatin, pravastatin: May be administered concomitantly with ferric citrate
Levofloxacin	No clinically meaningful interaction in vitro	May be administered concomitantly
Sitagliptin	No clinically meaningful interaction in vitro	May be administered concomitantly
Vitamin D analogs	Calcitriol, doxercalciferol: No clinically meaningful interaction in vitro	Calcitriol, doxercalciferol: May be administered concomitantly with ferric citrate
Warfarin	No clinically meaningful interaction in vitro	May be administered concomitantly

Ferric Citrate Pharmacokinetics

Absorption

Formal pharmacokinetic studies not performed. Changes in serum iron indices indicate iron from ferric citrate is systemically absorbed.

Stability

Storage

Oral

Tablets

20–25°C (may be exposed to 15–30°C). Protect from moisture.

Actions

Ferric iron binds dietary phosphate in GI tract, forming insoluble complex (ferric phosphate) that is excreted in feces.
Reduces serum phosphate concentration in dose-dependent manner.
Also alters serum iron indices, increasing ferritin, iron, and TSAT.
Clinical data suggest ferric citrate does not affect serum concentrations of folate or vitamins A, B₁₂, D, E, or K.

Advice to Patients

Importance of adhering to instructions about diet.
Importance of taking ferric citrate as directed with meals.
Importance of instructing patients about any concomitantly used drugs that should be taken at a different time of day than when ferric citrate is taken.
Potential for ferric citrate to cause discolored (dark) stools.
Potential for ferric citrate to cause diarrhea, nausea, constipation, and vomiting. Importance of reporting severe or persistent GI symptoms to clinician.
Risk of fatal iron poisoning in children <6 years of age. Importance of keeping ferric citrate out of reach of children. Contact a clinician or poison control center immediately in case of accidental overdosage.
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.
Importance of advising clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.
Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.