[Comparison of acute toxicity of two preparations of norcantharidin in mice].

OBJECTIVE To compare the acute toxicity of common injection and sustained-release preparation of norcantharidin for mice so as to identify the attenuation of the sustained-release preparation of norcantharidin. METHODS The poloxamer 407 was used as a sustained-release vehicle for topical administration of norcantharidin, and the acute toxicity of mice treated with common injection and sustained-release preparation of norcantharidin was observed. The median lethal dose (LD(50)) was calculated by Bliss software. RESULTS The symptoms of mice were similar between the two groups, but the appearance of symptoms in norcantharidin/poloxamer 407 group was 4 hours later than that in norcantharidin group. The LD(50) of norcantharidin administered through vein injection was 12.6 mg/kg. The LD(50) of norcantharidin/poloxamer 407 administered through intraperitoneal injection, intrahepatic injection and intramuscular injection were 19.9, 19.1 and 20.9 mg/kg, respectively, and the LD(50) of the common preparation were 13.0, 13.1 and 15.1 mg/kg, respectively. CONCLUSION The norcantharidin/poloxamer 407 is less toxic than the equivalent dose of norcantharidin, mainly because norcantharidin/poloxamer 407 may release norcantharidin sustainedly, thus reducing norcantharidin concentration in blood.