Objective To investigate the toxic reaction,toxic organs or target tissues of protamine recombinant human insulin (Insulin NPH),and provide basis for clinical trials by single dose toxicity test in mice,repeated toxicity and immunogenicity of Beagle's dogs,and systemic active allergy in guinea pig.Methods ① Using maximum dose method,mice in single dose toxicity test were sc injected with normal saline (NS),vehicle,and Insulin NPH (2092-2488 IU/kg),the toxic reactions after injection were monitored.② In repeated toxicity study,Beagle's dogs were sc administrated with vehicle,the original (Humulin NPH,1.5 IU/kg)and different doses of Insulin NPH (0.5,1.0 and 1.5 IU/kg) for 30 d continuously,followed by a 14-d recovery.During the administration and recovery period,general observation,local irritation,body weight,anus temperature,blood glucose,and electrocardiogram (ECG) were checked,moreover,hematology,serum biochemistry and urine were detected.Also,organic weights and histopathological examination were conducted.Binding antibodies in dog serum were measured by indirect ELISA method in immunogenicity test.③ In systemic active allergy study,cavies were sc injected with low-and high-dose (4 and 12 IU/kg) Insulin NPH,normal saline and vehicle.Besides,ova as positive control was also included.After five times of sensitization test with above doses,the excitation reactions of iv injection with tripled sensitizing doses were observed.Results No obvious toxicity was observed in mice after injected with 165 times of usual clinical dose of Insulin NPH.Repeated toxicity study of Beagle's dogs revealed that 1.0 IU/kg was the no-toxic-effect dose (NOAEL) for Insulin NPH,which was equivalent to 2 times of clinical dose.No bindingantibodies were found in immunogenicity test.There was no obvious allergic symptom in the active systemic allergy study of guinea pig.Conclusion Under the experimental conditions,no serious toxicity of Insulin NPH is found.