Acute Systemic Toxicity of Cyanides by Topical Application to the Eye

Abstract

The acute systemic toxicity of hydrogen cyanide and its sodium and potassium salts by instillation into the conjunctival sac was investigated. Using the rabbit, the LD50 values (with 95% confidence limits), in mmol/kg, with aqueous solutions instilled into the inferior conjunctival sac were determined to be 0.039 (0.036–0.042) for HCN, 0.103 (0.091–0.124) for NaCN, and 0.121 (0.100–0.138) for KCN. The acute lethal toxicity of NaCN was not significantly different when applied as solution or solid, and mixing the solid with an inert powder (kaolin) did not modify NaCN toxicity. For all preparations, signs of toxicity appeared rapidly and death occurred within 3 to 12 min of the eye being contaminated. Cyanide concentrations in blood, serum, and various tissues were measured, and the results found compatible with a diagnosis of death from acute cyanide poisoning. Thus, following their instillation into the conjunctival sac, cyanides may be absorbed in amounts sufficient to produce systemic toxicity. Contamination of the eye with cyanide could be a hazardous route of exposure.