The pharmacokinetics of the lymphotropic nanoparticle MRI contrast agent ferumoxtran-10

Ferumoxtran-10 is an ultrasmall superparamagnetic biodegradable iron oxide which serves as a MRI contrast agent in the differentiation of metastatic and non-metastatic lymph nodes in primary malignancies and imaging of phagocyte-associated disease processes. Ferumoxtran-10 is supplied as a lyophilized powder containing 210 mg of iron, 631 mg of dextran, and 27 mg of sodium citrate. The iron oxide core determines the magnetic properties of ferumoxtran-10, primarily its effects on the MR relaxation times, T1, T2, and T2*. Attachment of dextran prolongs the circulatory time of the nanoparticles. The intended human dose of ferumoxtran-10 is 2.6 mg Fe/kg. Reconstituted and diluted with physiological saline it is administered intravenously by means of a slow drip infusion. After initial vascular distribution of the particles, they are slowly phagocytosed by the reticuloendothelial system cells of the spleen, lymph nodes, bone marrow, and liver. When ferumoxtran-10 is present in phagocytic cells the iron oxide causes local magnetic field inhomogeneities which lead to increases in proton relaxation rates, resulting in signal loss on mid-T1/T2 or heavily T2-weighted MR images. Stored in lysosomes the particles are ultimately degraded: the iron enters the normal body iron metabolism cycle and dextran is eliminated mainly via the kidney.