Cyanide intoxication in sheep: enhancement of efficacy of sodium nitrite, sodium thiosulfate, and cobaltous chloride.

For treatment of cyanide intoxication of ruminants, the present recommended doses of sodium nitrite (5 mg/kg of body weight) and sodium thiosulfate (25 to 50 mg/kg) are smaller than those recommended for other animals; the decrease is partially attributed to the greater susceptibility of ruminants to the toxic effects of sodium nitrite. Based on the high tissue concentration and activity rate of rhodanese in ruminants, sulfur donors such as sodium thiosulfate could be utilized more efficaciously. Doses of sodium nitrite and sodium thiosulfate (up to 22 and 660 mg/kg, respectively) were evaluated in the present studies. Adjustment of the antidotal combination provided almost three times the protection afforded by the previously recommended doses. Moreover, under the conditions tested, the newly adjusted dose levels of sodium thiosulfate alone were more effective than the previously used antidotal combination of sodium nitrite and sodium thiosulfate and this protective effect was enhanced by cobaltous chloride (10.6 mg/kg) or sodium nitrite. The present recommended therapeutic approach to cyanide intoxication in sheep should be based primarily on administration of a much higher dose of sodium thiosulfate in combination with sodium nitrite or cobaltous chloride (or both).