title: Cyanide antidotes and methods of their administration in dogs: a comparative study.
abstract: To test the efficacies of various antidotes to cyanide (CN) poisoning, the lethal dose of cyanide in dogs was estimated during constant infusion of potassium cyanide at a rate of 0.1 mg/kg/min. Additionally, arterial blood pressure, right ventricular pressure, heart rate, electrocardiogram, blood-gas and pH values, and whole blood and tissue CN concentrations were measured. The lethal dose in animals whose lungs were ventilated with room air was 2.4 +/- .2 mg/kg (mean +/- SE), while the whole-blood CN concentration was 438 +/- 40 micrograms/dl and the gracilis muscle concentration was 2.0 +/- .3 micrograms/100 g. A low dose of vitamin B12a (100 mg/kg), an infusion of thiosulfate (12 mg/kg/h), or ventilation with 100 per cent O2 increased the amount of CN needed to cause death. A bolus injection of nitrite (5 mg/kg), thiosulfate (150 mg/kg), or cysteine (450 mg/kg) increased the the protection from lethality even further. Protection against CN administration for the total 150-min period of observation was provided by a bolus injection plus a constant infusion of nitrite (5 mg/kg bolus plus 5 mg/kg/h). thiosulfate (30 mg/kg bolus plus 60 mg/kg/h), or vitamin B12a (50 mg/kg bolus plus 100 mg/kg/h). However, nitrite infusion produced high levels of methemoglobin 7.2 +/- 1.1 g/dl, while vitamin B12a infusion and cysteine injection, at the stated doses, did not prevent cyanide-induced circulatory failure. Therefore, thiosulfate appears to be the most effective and safest prophylactic agent against cyanide toxicity in dogs.
mesh_terms: D000678:Amygdalin / Q000506:poisoning; D000818:Animals; D000931:Antidotes; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000187:drug effects; D003486:Cyanides / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000506:poisoning*; D003545:Cysteine / Q000627:therapeutic use; D004285:Dogs; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D009573:Nitrites / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D013885:Thiosulfates / Q000494:pharmacology; D014805:Vitamin B 12 / Q000494:pharmacology
chemical_list: D000931:Antidotes; D003486:Cyanides; D009573:Nitrites; D013885:Thiosulfates; D000678:Amygdalin; D003545:Cysteine; D014805:Vitamin B 12; D010100:Oxygen