Study On Safety Evaluation Of Fipronil Nanoemulsion

Along with the development of our national economy and pet industry,fipronil as a new type of phenyl pyrazole insecticides has been widely used for the prevention and treatment of pet parasites.This study was set to evaluate the safety of fipronil nanoemulsion in animals and provide reliable data for its clinical application.The specific studies were as follows:1.The irritation of fipronil nanoemulsion on the skin of rabbitsTo study the irritation of fipronil nanoemulsion on the skin of rabbits,8 rabbits were randomly divided into intact skin group and damaged skin group with half male and half female.0.5 mL fipronil nanoemulsion or saline was applied to each group for 8 h.Observation and score at 1 h?24 h?48 h?72 h after drug withdraw.Local tissue slices were made when stimulate reached moderate.The results showed that the score was 0 and there was no stimulation.It suggests that there is no stimulationin in rabbits administered via skin with fipronil nanoemulsion at the clinical dosage.2.The acute oral toxicity of fipronil nanoemulsionTo study the acute oral toxicity of fipronil nanoemulsion,20 SD rats were administered via oral with 0.25%fipronil nanoemulsion at the dose of 1 mL·100g-1 and administered via oral with the drug again at the dose of 0.5 mL 100g-1 after 6 h.The death and toxic reaction in rats were observed.The results showed that 3 rats died with obvious toxic symptoms during the period of experiment.LD50 of the fipronilna noemulsion orally administered in rats was greater than 15 mL·kg-1,equivalent of 37.5 mg·kg-1 fipronil.The results indicated that the toxicity of the drug was high according to the acute toxicity dose fractionation of chemicals.3.The percutaneous acute toxicity of fipronil nanoemulsionTo study the percutaneous acute toxicity of fipronil nanoemulsion in rats,40 SPF SD rats were chosen and randomly divided into two groups,the experimental group and the blank solvent control group,with half male and half female.Fipronil nanoemulsion was administered and coated at the dose of 2 000 mg·kg-1·bw on the hair removed area for 24 h.Rats were weighted before administration and 7 d and 14 d after administration,the toxicity and death of rats were observed during the experiment.The results showed that there was toxic reaction but no death in rats.It suggests that the minimum lethal dose of fipronil nanoemulsion was greater than 2 000 mg·kg-1·bw in rats through the percutaneous administration and the drug was low toxicity according to the skin toxicity grading criteria.4.The pharmacokinetics of fipronil nanoemulsion in dogs via transdermal administrationTo establish a detection method with fipronil by reversed-phase HPLC in dog plasma and detect the pharmacokinetics of fipronil nanoemulsion administrated transdermally in healthy dogs,8 healthy dogs were administrated the drug transdermally at the dose of 6 mL·kg-1.The plasma samples were treated with acetone and the concentration of fipronil in plasma of dogs was detected by reversed-phase HPLC.3p97 pharmacokinetics software was used to analysis the data of plasma drug concentration versus time.The results showed a good linear relationship of fipronil within 0.05 to 4 ?g·mL-1 in plasma.The correlation coefficient R2=0.999.The detectability was 0.01 ?g·mL-1.The limit of quantification was 0.05 ?g·mL-1.Absolute recovery from plasma was higher than 90%and both the variation within and between days were less than 10%.The fipronil was not detected in the plasma of dogs after administration.It suggests that the determination method of fipronil in dog plasma by reversed-phase HPLC was convenient,specific,sensibility and can be free from the interference of impurity peak in plasma.The results indicated that the absorbtion of fipronil nanoemulsion through skin was less and safety.5.The safety evaluation of fipronil nanoemulsion in dogsTo study the safety of fipronil nanoemulsion in dogs and provide scientific basis for its clinical application,24 Springer Spaniels were randomly divided into the recommended dose group(6 mL·kg-1·bw),3-fold dose group(18 mL·kg-1·bw),5-fold dose group(30 mL·kg-1·bw)and control group with no drugs.The treatment groups were dosed one time a day by spray administration for 4 days continuously.Take the blood in the morning of 0,3,5 days after treatment(fasting overnight)for determination of the routine blood and blood biochemical tests.The clinical symptoms during the test and the changes of pathological anatomy and histology at the end of the test were observed.The results showed that no toxicity reaction,no obvious physiological and biochemical indexes change and no obvious organization structure effect in dogs administrated with 1,3,5 fold dose of clinical recommend dosage fipronil nanoemulsion for continued 4 days.It suggests that fipronil nanoemulsion is safe according to recommended clinical dose in dogs.