In vivo release of cyanide from sodium nitroprusside

Brain cytochrome oxidase activity was measured after the in vitro addition of potassium cyanide (KCN) or sodium nitroprusside (SNP). Activity of cytochrome oxidase was sensitive to KCN; however, this activity was unaffected by SNP. In SNP- and KCN-treated animals brain cytochrome oxidase activities were measured. At 3 min after SNP injection, inhibition of the enzymatic activity was the same as 1 min after KCN injection. Time to death for SNP-treated animals was longer than for KCN-treated animals. These data suggest that cyanide was released in vivo from SNP and that time was necessary for this release to occur.