Further investigations regarding the toxicity of sodium nitroprusside

Sodium nitroprusside is a valuable vasodilator, but its use has been curtailed because of numerous reports that, in the presence of blood, nitroprusside decomposes with release of toxic cyanide. We have examined the release of cyanide in terms of the known chemistry of nitroprusside and suggest that photochemical decomposition of nitroprusside and (or) its metabolism in vivo invalidates the analytical procedure used by previous workers. We also present evidence for the stability of nitroprusside in blood, based on 13C nuclear magnetic resonance studies.