OBJECTIVE To evaluate the safety of epinephrine hydrochloride injection(EHI) given by nebulized inhalation in guinea pigs with the off-label drug use. METHODS The actual dose of inhalation administration was determined by establishing a nebulized administration drug concentration assay. The systemic allergic reactions and respiratory toxicity of EHI after nebulized inhalation were evaluated by guinea pigs using the allergy test protocol with the combination of frequency and dose of epinephrine hydrochloride administration and allergy test. Thirty-two guinea pigs were randomly divided into 4 groups according to body weight: negative control group(equal volume of saline), positive control group(sensitizing dose: 20 mg·kg-1 ovalbumin), low dose group(sensitizing dose: 15.5 μg·kg-1 EHI) and high dose group(sensitizing dose: 31 μg·kg-1 EHI). The excitation dose of each group was two times the sensitization dose, at the time of excitation, the symptoms of allergic reaction were observed. After excitation, blood and alveolar lavage fluid were collected, whole blood was collected for hematological testing and isolated serum and alveolar lavage fluid were used for IgE testing. Bronchial and lung tissues were taken for histological testing and immunohistochemistry after dissection. RESULTS Using a nebulizer device to administer EHI to guinea pigs at a clinically equivalent dose at 3.95 min of administration. The guinea pigs in all groups showed normal weight gain during sensitization administration. At the time of excitation, the guinea pigs in the positive control group showed strong positive allergic reactions, while the guinea pigs in the negative control group, low dose group and high dose group showed no significant allergic reactions. Compared with the negative control group, eosinophils in the blood of the positive control guinea pigs were significantly higher(P<0.05) and the IgE content in the serum and alveolar lavage fluid was significantly increased(P<0.05 or P<0.01). Histopathological results showed that inflammatory cells infiltrated in the lung tissue of the positive control guinea pigs after excitation, and a large number of erythrocytes and exudate appeared in the alveoli. The immunohistochemical indiacated that the inflammatory symptoms in the lung tissues of the positive guinea pigs were associated with an increase in B lymphocytes. The hematological indexes, serum IgE content, immunohistochemical and histological examination results of guinea pigs in the low and high dose groups were not significantly different from those of the negative control group. CONCLUSION No allergic reaction and no respiratory toxicity occurred in guinea pigs given EHI by nebulization, and the administration of EHI by nebulized inhalation off-label drug use is safe and feasible.