Ferric citrate Other names: Iron(III) citrate

Hyperphosphatemia in Chronic Kidney Disease on Dialysis

Ferric iron binds dietary phosphate in the GI tract and precipitates as ferric phosphate. This compound is insoluble and is excreted in the stool. By binding phosphate in the GI tract and decreasing absorption, ferric citrate lowers the phosphate concentration in the serum.

Iron Deficiency Anemia in Chronic Kidney Disease Not On Dialysis

Ferric iron is reduced from the ferric to the ferrous form by ferric reductase in the GI tract. After transport through the enterocytes into the blood, oxidized ferric iron circulates bound to the plasma protein transferrin, and can be incorporated into hemoglobin.

Hyperphosphatemia in Chronic Kidney Disease on Dialysis

Ferric citrate reduces serum phosphorus levels and has also been shown to increase serum iron parameters, including ferritin, iron and TSAT. In dialysis patients treated with ferric citrate for hyperphosphatemia in a 52-week study in which intravenous iron could also be administered, mean (SD) ferritin levels rose from 593 (293) ng/mL to 895 (482) ng/mL, mean (SD) TSAT levels rose from 31% (11) to 39% (17) and mean (SD) iron levels rose from 73 (29) mcg/dL to 88 (42) mcg/dL. In contrast, in patients treated with active control, these parameters remained relatively constant.

Iron Deficiency Anemia in Chronic Kidney Disease Not On Dialysis

Ferric citrate may increase hemoglobin levels and has also been shown to reduce serum phosphorus levels. In chronic kidney disease patients not on dialysis treated with ferric citrate for iron deficiency anemia in a 16-week placebo-controlled study, mean (SD) phosphorus levels decreased from 4.23 (0.91) mg/dL at baseline to 3.72 (0.60) mg/dL. In comparison, in patients treated with placebo control, mean (SD) phosphorus levels decreased from 4.12 (0.68) mg/dL at baseline to 3.87 (0.68) mg/dL.

Absorption and Distribution

Formal pharmacokinetic studies have not been performed with ferric citrate. Examination of serum iron parameters has shown that there is systemic absorption of iron from ferric citrate.

Drug Interaction Studies

In vitro

Of the drugs screened for an interaction with ferric citrate in vitro, only doxycycline showed the potential for interaction with at least 70% decrease in its concentration. This interaction can be avoided by spacing the administration of doxycycline and ferric citrate.

In vivo

Six drug interaction studies (N=26-60/study) were conducted to establish the effects of ferric citrate (administered as 3 × 2 g/day with meals) on the disposition of concomitantly orally administered clopidogrel, ciprofloxacin, digoxin, diltiazem, glimepiride and losartan in healthy subjects. With the exception of ciprofloxacin, ferric citrate did not alter the systemic exposure of the tested drugs, as measured by the area under the curve (AUC) and C_max of the tested drugs when either co-administered with ferric citrate or given 2 hours later. Ferric citrate decreased the relative bioavailability of concomitantly administered ciprofloxacin by approximately 45%. However, there was no interaction when ferric citrate and ciprofloxacin were taken 2 hours apart. Consequently, ciprofloxacin should be taken at least 2 hours before or after ferric citrate is dosed.