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Ferric Citrate Approved As Phosphate Binder for Dialysis Patients

Cheryl A. Thompson

Keryx Biopharmaceuticals Inc. on Friday announced that FDA had approved the marketing of the company's ferric citrate tablets as a means of controlling the serum phosphorus concentration in patients with chronic kidney disease who are undergoing dialysis.

The drug's ferric ion binds to dietary phosphate in the gastrointestinal tract to form ferric phosphate, which is excreted in patients' stool. By preventing absorption of phosphate, the drug lowers patients' serum phosphorus concentration.

According to the product's FDA-approved labeling (PDF)External Link, the starting dosage of ferric citrate is two tablets taken three times daily with meals. The dosage can be increased or decreased by one or two tablets at one-week or longer intervals to control a patient's serum phosphorus concentration. No more than 12 tablets should be taken in one day.

Ferric ion can bind to anions other than phosphate. The labeling states that doxycycline doses should be taken at least one hour before ferric citrate tablets. In general, the labeling advises clinicians to consider separating the time of administration of ferric citrate from the administration time of any oral medication whose bioavailability could be reduced by ferric ion and consequently have a "clinically significant effect" on safety or effectiveness.

Some of the iron in ferric citrate may be absorbed from patients' gastrointestinal tract. The drug is contraindicated in patients with an iron overload syndrome, such as hemochromatosis. Clinicians are told in the labeling's Warnings and Precautions section to assess patients' iron status before starting ferric citrate therapy and also monitor iron status during therapy.

During clinical trials of the drug, the most common adverse events in patients who received ferric citrate were diarrhea, nausea, constipation, vomiting, and cough.

The new phosphate binder will be available in 200-count bottles labeled as containing ferric iron 210-mg tablets. Each 210-mg film-coated tablet is the equivalent of 1 g of ferric citrate. The tablets should be protected from moisture and stored at 20–25 °C.

Keryx said its ferric citrate tablets may have a U.S. brand name by the time the product becomes available to patients.

The company's chief executive officer said the product will be on the market within 12 weeks.

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