Thiocyanate from sodium nitroprusside

HCN is detoxified to thiocyanate (SCN ) by the mitochondrial enzyme rhodanese rhodanese catalyzes the transfer of sulfur from thiosulfate to cyanide to yield thiocyanate, which is relatively nontoxic (Smith 1996). The rate of detoxification of HCN in humans is about 1 pg/kg/min (Schulz 1984) or 4.2 mg/h, which, the author states, is considerably slower than in small rodents. This information resulted from reports of the therapeutic use of sodium nitroprusside to control hypertension. Rhodanese is present in the liver and skeletal muscle of mammalian species as well as in the nasal epithelium. The mitochondria of the nasal and olfactory mucosa of the rat contain nearly seven times as much rhodanese as the liver (Dahl 1989). The enzyme rhodanese is present to a large excess in the human body relative to its substrates (Schulz 1984). This enzyme demonstrates zero-order kinetics, and the limiting factor in the detoxification of HCN is thiosulphate. However, other sulfur-containing substrates, such as cystine and cysteine, can also serve as sulfur donors. Other enzymes, such as 3-mercapto-pyruvate sulfur transferase, can convert... 

Thiocyanate in blood 40 (rg/l 00 mL in control nonsmokers 100 (rg/l00 mL in control smokers 420 (ig/100 mL in cyanide-exposed nonsmokers 480 pg/100 mL in cyanide-exposed smokers Maehly and Swensson (1970) Found no relationship between exposure and blood cyanide levels Blood CN—of control nonsmokers ranged from 3.5-10.1 pg/100 mL Blood CN—of control smokers ranged from 2.0-13.0 pg/100 mL Blood CN—of control and cyanide-exposed workers combined ranged from 2.0-15 pg/100 mL (Separate data were not provided for cyanide workers) Aitken et al. (1977) Male and female patients, ages 13-66, presurgery mean 2.7 pg/100 mL Following infusion of sodium nitroprusside 13-205 pg/100 mL Metabolic acidosis at >90 pg/100 mL Nitroprusside doses 12-783 pg/kg (0.8-9.8 pg/kg/min over durations of 15 to 86 min) ... 

Thiocyanate [SCN ], the anion of thiocyanic acid, is an important waste product from the chemical industry, it is present in various food items, it may be added to dairy milk to promote bacteriostatic processes, and it is synthesixed in the human liver as part of detoxification of cyanide. A special case in medicine has been generation of large amounts of thiocyanate leading to hypothyroidism after sodium nitroprusside infusion for hypertension (Nourok et at, 1964). After oral ingestion thiocyanate is readily absorbed. It is partly bound to albumin in blood, and mainly eliminated by excretion in urine. The half life of thiocyanate in humans is in the order of 1—2 weeks (Scherer, 2006), but varies between individuals. Thiocyanate may have a number of... 

Votocek-Dubsky s method is based on the property exhibited by some mercuric salts to be very poorly ionized in solution because they actually are complexes. This property is shared by halide, cyanide, and thiocyanate ions. Oxygenated salts, however, are normally ionized (nitrate, sulfate). From another standpoint, sodium nitroprusside forms a white precipitate of mercuric nitroprusside with Hg + ions, that is, with oxygenated mercuric salts but not with halides or parent compounds because of their property of being complexes. The principle of Votocek s method results from these considerations (see Fig. 27.1). 

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