The present invention describes a method of sequestering nitric oxide from the bloodstream, endothelium or tissues of mammals by administering a cobalamin to such mammals. A method of treating diseases characterized by elevated nitric oxide levels in the bloodstream, endothelium or tissues is further provided. In particular, a method of treating sepsis by administering a therapeutic dose of hydroxocobalamin is described by the present invention. A method of alleviating systemic hypotension in a septic patient is further described by this invention. A pharmaceutical composition comprising a cobalamin in a concentration ranging from 0.5 to 50 mg composition/Kg body weight for mammals and is also provided.