A Comparison of the Treatment of Cyanide Poisoning in the Cynomolgus Monkey with Sodium Nitrite of 4-Dimethylaminophenol (4-DMAP), with and without Sodium Thiosulfate

Two methemoglobin generating compounds, sodium nitrite (iv) or 4- dimethylaminophenol (4-DMAP (im), with and without sodium thiosulfate (iv), were compared as post-treatment therapy in anesthetized monkeys poisoning with cyanide. Arterial blood samples were taken before and after an injection of sodium cyanide (8.4 mg/kg) and treatment for analyses of blood cyanide, plasma cyanide, thiocyanate and methemoglobin content. Physiologic parameters were monitored in these treated cyanide-poisoned animals. The time course of methemoglobin formation and physiologic parameters were also monitored in animals receiving only 4-DMAP or sodium nitrite. A maximal methemoglobin level was observed at 30 minutes following injection of 4-DMAP, and 60 minutes post injection with sodium nitrite. Volumes of distribution (Vd) of cyanide were calculated from the concentrations of cyanide in blood samples and doses of cyanide injected. Although 4-DMAP forms methemoglobin more rapidly than sodium nitrite, both compounds form methemoglobin quickly enough to provide protection against cyanide poisoning. The protection offered by either compound against the lethal effects of cyanide was potentiated when used in combination with sodium thiosulfate. Cyanide, Sodium nitrite, 4-Dimethylaminophenol, Sodium thiosulfate, Thiocyanate, Methemoglobin.