Comparative evaluation of acute toxicity of ivermectin by two methods after single subcutaneous administration in rats.

Ivermectin was evaluated for its acute toxicity after single subcutaneous (s/c) administration by 'Acute Toxic Class' method as per OECD 423 and by conventional acute toxicity test using probit analysis in rats. 'Acute toxic class' method yielded LD(50) in category 2 i.e. between 5 and 50mg/kg which was comparable with conventional method where it was found to be 51.5mg/kg. Post mortem lesions were observed in the form of congestion of liver, which showed centrilobar necrosis and hemorrhages on histopathological analysis in both the methods. This study suggests, 'Acute Toxic Class' method may be used instead of conventional method to study acute toxicity of injectable preparations. Similarly the LD(50) of around 50mg/kg indicated a wide margin of safety (250x) considering therapeutic dose of ivermectin as 200microg/kg.