Some metabolic effects of sodium nitroprusside in man.

The infusion of sodium nitroprusside during surgical operations produced plasma levels of cyanide of up to four times the control value. Plasma thiocyanate showed little change except during prolonged infusion of the drug, but total plasma B(12) tended to fall, as did methylcobalamin. Other cobalamins showed little change after nitroprusside infusion for short periods. During longer infusions the ratio of methylcobalamin to adenosyl + hydroxocobalamin fell and cyanocobalamin concentrations were high.