» Ferumoxides Injection is a sterile colloidal suspension of superparamagnetic iron oxide associated with dextran in Water for Injection. It contains not less than 95 percent and not more than 105 percent of the labeled amount of iron. It contains in each mL not less than 5.6 mg and not more than 9.1 mg of dextran. It contains in each mL not less than 0.25 mg and not more than 0.53 mg of citrate. It also contains mannitol. It contains no antimicrobial agents. Ferumoxides is a nonstoichiometric iron oxide magnetite of average formula FeO_1.44, with particles having a diameter between 100 and 250 nm.