Compounds and methods for utilizing compounds comprising a superoxide dismutase mimetic covalently linked to polyethylene glycol. Methods are also provided for preparing a superoxide dismutase mimetic covalently linked to a polyethylene glycol, the methods comprising reacting an activated polyethylene glycol with a superoxide dismutase mimetic, or alternatively, reacting a superoxide dismutase mimetic with an activated polyethylene glycol. A method is also provided for preventing or treating a disease or disorder in which superoxide anions are implicated, comprising administering to a subject in need thereof, a therapeutically effective amount of a compound comprising a superoxide dismutase mimetic covalently linked to a polyethylene glycol. Methods of determining the safety and efficacy of the compounds are also provided. Methods for determining the safety and efficacy can include methods in lab animals and humans.