Formation of cyanide from o-chlorobenzylidene malononitrile and its toxicological significance

Mice received o-chlorobenzylidene malononitrile (CS) by i.p. injection (0.5 LD₅₀) or by aerosol exposure (20,000 mg min^–1 m^–3). Increased excretion of thiocyanate in the urine was observed, indicating a transformation of CS to cyanide in vivo. Determinations of cyanide in whole blood after i.p. administration of CS verified a rapid transformation of the agent to cyanide. A correlation between the time course of cyanide levels and symptoms was observed. Toxicity of injected CS was significantly reduced by pretreatment with thiosulfate, slightly reduced by nitrite and not affected by Co₂EDTA.Thiocyanate excretion, blood cyanide levels and protective effect of antidotes were also evaluated after administration of 0.5 LD₅₀ of malononitrile and potassium cyanide. The importance of cyanide formation for the toxicity of CS is discussed.