Abstract: AIM: To investigate the effects of age, gender, duration of medication and combined medication on the steady-state blood concentration of tacrolimus in patients with autoimmune diseases, and to establish the reference range of steady-state blood concentration of tacrolimus in combination with liver and kidney function, so as to provide theoretical basis for clinical individual medication.  METHODS: A total of 107 patients with autoimmune diseases treated with tacrolimus in the department of rheumatology and immunology of our hospital from August 2017 to June 2021 were included. Their gender, age, dose, drug combination, blood concentration, and liver and kidney function were statistically analyzed by SPSS 22.0 statistical software. RESULTS: In the treatment of autoimmune diseases with tacrolimus, there was statistical significance in the blood concentration of different genders (P<0.05), but there was no statistical significance in the blood concentration of different ages (P>0.05) and a statistically significant difference in the dosage of tacrolimus (P<0.05), the duration of medication did not affect the effective dose, target blood concentration, liver and kidney functions. There was a weak correlation between tacrolimus dose and blood concentration (r=0.115, P=0.047). When the blood concentration of tacrolimus ranged from 4.20 to 9.48 ng/mL, the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and urea increased significantly. When tacrolimus blood concentration ranged from 0.08 to 4.20 ng/mL, there was no significant difference in serum creatinine, AST, ALT, albumin, total bilirubin (TBIL), direct bilirubin (DBIL), indirect bilirubin (IBIL). CONCLUSION: Tacrolimus is used for the treatment of autoimmune diseases, and the blood concentration varies greatly among individuals. To avoid the risk of potential damage to liver and kidney function. It is recommended that clinicians control the blood concentration at 0.08-4.20 ng/mL, and adjust the dose and optimize the dose according to the patient's gender, age, and clinical efficacy.

Key words: tacrolimus, autoimmune disease, blood concentration, liver function, kidney function