Cyanide acts primarily through its strong affinity for the iron-containing heme moiety, binding to numerous critical enzyme systems in the body and rendering them inactive. Of late, increasing attention has been paid to the relationship of cyanide and nitric oxide. The interactions appear to be complex, with cyanide inducing nitric oxide production by binding to N-methyl-D-aspartate (NMDA) receptors, as well as binding to nitric oxide synthase. The latter may be overcome by the presence of nitric oxide synthase inhibitors.