12.1 Mechanism of Action

Venofer is an aqueous complex of poly-nuclear iron (III)-hydroxide in sucrose. Following intravenous administration, Venofer is dissociated into iron and sucrose and the iron is transported as a complex with transferrin to target cells including erythroid precursor cells. The iron in the precursor cells is incorporated into hemoglobin as the cells mature into red blood cells.

12.2 Pharmacodynamics

Following intravenous administration, Venofer is dissociated into iron and sucrose. In 22 patients undergoing hemodialysis and receiving erythropoietin (recombinant human erythropoietin) therapy treated with iron sucrose containing 100 mg of iron, three times weekly for three weeks, significant increases in serum iron and serum ferritin and significant decreases in total iron binding capacity occurred four weeks from the initiation of iron sucrose treatment.

12.3 Pharmacokinetics

In healthy adults administered intravenous doses of Venofer, its iron component exhibited first order kinetics with an elimination half-life of 6 h, total clearance of 1.2 L/h, and steady state apparent volume of distribution of 7.9 L. The iron component appeared to distribute mainly in blood and to some extent in extravascular fluid. A study evaluating Venofer containing 100 mg of iron labeled with 52Fe/59Fe in patients with iron deficiency showed that a significant amount of the administered iron is distributed to the liver, spleen and bone marrow and that the bone marrow is an irreversible iron trapping compartment.

Following intravenous administration of Venofer, iron sucrose is dissociated into iron and sucrose. The sucrose component is eliminated mainly by urinary excretion. In a study evaluating a single intravenous dose of Venofer containing 1,510 mg of sucrose and 100 mg of iron in 12 healthy adults (9 female, 3 male: age range 32 to 52), 68.3% of the sucrose was eliminated in urine in 4 h and 75.4% in 24 h. Some iron was also eliminated in the urine. Neither transferrin nor transferrin receptor levels changed immediately after the dose administration. In this study and another study evaluating a single intravenous dose of iron sucrose containing 500 to 700 mg of iron in 26 patients with anemia on erythropoietin therapy (23 female, 3 male; age range 16 to 60), approximately 5% of the iron was eliminated in urine in 24 h at each dose level. The effects of age and gender on the pharmacokinetics of Venofer have not been studied.

Pharmacokinetics in Pediatric Patients

In a single-dose PK study of Venofer, patients with NDD-CKD ages 12 to 16 (N=11) received intravenous bolus doses of Venofer at 7 mg/kg (maximum 200 mg) administered over 5 minutes. Following a single dose of Venofer, the half-life of total serum iron was 8 hours. The mean Cmax and AUC values were 8545 μg/dl and 31305 hr•μg/dL, respectively, which were 1.42- and 1.67-fold higher than dose adjusted adult Cmax and AUC values.

Venofer is not dialyzable through CA210 (Baxter) High Efficiency or Fresenius F80A High Flux dialysis membranes. In in vitro studies, the amount of iron sucrose in the dialysate fluid was below the levels of detection of the assay (less than 2 parts per million).