Evaluation of the Physicochemical Properties of the Iron Nanoparticle Drug Products: Brand and Generic Sodium Ferric Gluconate

Mol Pharm. 2021 Apr 5;18(4):1544-1557. doi: 10.1021/acs.molpharmaceut.0c00922. Epub 2021 Feb 23.


Complex iron nanoparticle-based drugs are one of the oldest and most frequently administered classes of nanomedicines. In the US, there are seven FDA-approved iron nanoparticle reference drug products, of which one also has an approved generic drug product (i.e., sodium ferric gluconate (SFG)). These products are indicated for the treatment of iron deficiency anemia and are administered intravenously. On the molecular level, iron nanomedicines are colloids composed of an iron oxide core with a carbohydrate coating. This formulation makes nanomedicines more complex than conventional small molecule drugs. As such, these products are often referred to as nonbiological complex drugs (e.g., by the nonbiological complex drugs (NBCD) working group) or complex drug products (e.g., by the FDA). Herein, we report a comprehensive study of the physiochemical properties of the iron nanoparticle product SFG. SFG is the single drug for which both an innovator (Ferrlecit) and generic product are available in the US, allowing for comparative studies to be performed. Measurements focused on the iron core of SFG included optical spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), X-ray powder diffraction (XRPD), 57Fe Mössbauer spectroscopy, and X-ray absorbance spectroscopy (XAS). The analysis revealed similar ferric-iron-oxide structures. Measurements focused on the carbohydrate shell comprised of the gluconate ligands included forced acid degradation, dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and gel permeation chromatography (GPC). Such analysis revealed differences in composition for the innovator versus the generic SFG. These studies have the potential to contribute to future quality assessment of iron complex products and will inform on a pharmacokinetic study of two therapeutically equivalent iron gluconate products.

Keywords: colloidal iron carbohydrate drugs; generic nanoparticles; iron nanoparticle; nanomedicine; non-biologic complex drugs; physicochemical properties; sodium ferric gluconate.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anemia, Iron-Deficiency / drug therapy
  • Chemistry, Pharmaceutical
  • Chromatography, Gel
  • Drugs, Generic / administration & dosage
  • Drugs, Generic / chemistry*
  • Drugs, Generic / pharmacokinetics
  • Drugs, Generic / standards
  • Dynamic Light Scattering
  • Equivalence Trials as Topic
  • Ferric Compounds / administration & dosage
  • Ferric Compounds / chemistry*
  • Ferric Compounds / pharmacokinetics
  • Ferric Compounds / standards
  • Humans
  • Nanoparticles / administration & dosage
  • Nanoparticles / chemistry*
  • Nanoparticles / standards
  • Quality Control
  • Ultracentrifugation


  • Drugs, Generic
  • Ferric Compounds
  • ferric gluconate