Following the previous study, the toxicity of a single subcutaneous administration of the Thyrokitty injection (I-131) and the side effects that may occur at therapeutic doses were confirmed. The Thyrokitty injection (I-131) was administered subcutaneously once at a dose of 0, 2.0, 6.0, and 18.0 mCi/kg, 5 male and female rats per group, and mortality, general symptom observation, and weight measurement were performed for 2 weeks, followed by observation of autopsy findings. There were no deaths, and no statistically significant weight change was observed. Mild hair loss, fissures, and crusting were observed by general symptom observation, but it was not a toxic change related to the Thyrokitty injection (I-131). Gastric atrophy and a decrease in the size of the spleen were observed by the autopsy. As a results of single subcutaneous administration of the Thyrokitty Injection (I-131) to rats at a maximum dose of 18.0 mCi/kg, a decrease in the size of the spleen and gastric atrophy were observed as the dose of the Thyrokitty Injection (I-131) increased, which may be related to the test substance. No abnormal findings related to the Thyrokitty injection (I-131) were observed. Therefore, the approximate lethal dose of the Thyrokitty injection (I-131) was 18.0 mCi/kg or more. In addition, as reported for the treatment of feline hyperthyroidism with radioiodine (131I), side effects of the Thyrokitty injection (I-131) are expected to be extremely rare. Temporary dysphagia and fever may occur, but it will recover naturally. It should be administered with caution in cats with diseases such as urinary system, cardiovascular system, gastrointestinal system and endocrine system, especially with kidney disease. And it should not be used in cats who are pregnant, lactating, or likely. It is expected that the Thyrokitty injection (I-131) can be used for clinical treatment in Korea as a veterinary drug.

Abstract
INTRODUCTION
MATERIALS AND METHODS
    시험방법 개요
    시험물질의 품질 확인 시험
    시험물질 조제 및 투여
    실험동물 사육 관리
    실험 설계
    관찰 및 측정
    부검
    통계 분석
RESULTS
    시험물질의 품질 확인 및 투여
    사망률
    일반증상
    체중
    부검 소견
DISCUSSION
SUPPLEMENTARY MATERIALS
REFERENCES

• Jae Cheong Lim(Radioisotope Research Division, Korea Atomic Energy Research Institute) Corresponding author
• Da Mi Kim(Radioisotope Research Division, Korea Atomic Energy Research Institute)
• Sung Soo Nam(Radioisotope Research Division, Korea Atomic Energy Research Institute)
• Eun Ha Cho(Radioisotope Research Division, Korea Atomic Energy Research Institute)
• So-Young Lee(Radioisotope Research Division, Korea Atomic Energy Research Institute)
• Hye Kyung Chung(Korea Radioisotope Center for Pharmaceuticals, Korea Institute of Radiological and Medical Sciences)
• Inki Lee(Korea Radioisotope Center for Pharmaceuticals, Korea Institute of Radiological and Medical Sciences)