Objective To understand the usage of antibiotics in outpatients in a county of Zhejiang Province from 2015 to 2020， so as to provide a basis for further standardizing the clinical application of antibiotics in this region.

Methods Outpatient records and prescription records of 146 public medical institutions from 2015 to 2020 were extracted from the electronic medical record data sharing platform system of medical institutions in a county of Zhejiang Province. The utilization rates and the number of types of antibiotics used in outpatient patients were described. According to the drug anatomy， therapeutic and chemical classification system （ATC）， clinical application classification and dosage form， the use status of different types of antibiotics was observed. The annual percentage change （APC） was used to analyze the time trend of antibiotic use. Among the antibiotic prescriptions in each year， the proportions of prescriptions aimed for different use reasons and patients were compared to analyze the changes in the structures of antibiotic prescriptions.

Results During 2015‒2020， a total of 2 861 438 prescriptions were issued in 146 primary public medical institutions in this county， including 314 642 prescriptions for antibiotics， and the overall utilization rate of antibiotics was 11%. The utilization rate of antibiotics showed a decreased trend across the years （from 14.23% in 2015 to 7.59% in 2020， APC=-11.51%， 95%CI=-0.01%‒-21.7%， t=-12.05， P<0.001） and an obvious seasonal variation character （higher in winter and spring， lower in summer and autumn）. Cefoxitin sodium for injection was the most used antibiotic in 2015， and cefuroxime was the most used antibiotic from 2015 to 2020， respectively. The utilization rates of cephalosporins （APC=-11.06%， 95%CI=0‒-20.89%， t=-22.233， P<0.001）， quinolones （APC=-9.74%， 95%CI=0‒-18.53%， t=-7.652， P=0.002）， macrolides （APC=-17.52%， 95%CI=0‒-17.52%， t=-3.626， P=0.022） and lincoamides （APC=-49.01%， 95%CI=0‒-74%， t=-3.35， P=0.029） showed a decreasing trend across the years. There were differences in the distribution of drug use reasons （χ²=9 458.427， P<0.001）， as well as the age （χ²=5 421.709， P<0.001） and sex （χ²=245.322， P<0.001） of patients. During the observation period， 50.69% of antibiotic prescriptions were used to treat respiratory diseases， with the highest proportion of 57.67% in 2015 and the lowest proportion of 34.93% in 2020. 58.37% of patients were aged 50‒70 years， with a decreasing proportion of patients under 50 years （17.83% in 2015， 6.64% in 2020） and an increasing proportion of patients over 70 years （24.1% in 2015， 38.41% in 2020）.

Conclusion The utilization rate of antibiotics used in outpatients from primary public medical institutions in a county of Zhejiang Province shows a decreasing trend across the years， but higher than that of secondary and above hospitals in China， and also higher than that of primary medical institutions in economically-developed areas. The management and monitoring of the clinical use of antibiotics in the county should be actively strengthened.