Regional Variation of Antimicrobial Use in Japan from 2013-2016, as Estimated by the Sales Data

The National Action Plan on Antimicrobial Resistance in Japan aims to achieve a 50% reduction in the use of broad-spectrum oral antimicrobials (cephalosporins, macrolides, and quinolones) from 2013 to 2020. Based on the national sales data for antimicrobials, we estimated the regional antimicrobial use (AMU) from 2013-2016 and evaluated the differences in the use of broad-spectrum oral antimicrobials among three regions in which differences had been identified previously. The AMU was standardized based on the defined daily dose (DDD) and described as the DDDs/1,000 inhabitants/day (DID). Annual combined total oral and parenteral AMU during 2013-2016 was 14.9, 14.5, 14.7, and 14.6 DID, respectively. The change in mean ± standard deviation in the total AMU at the prefectural level was - 0.2 ± 0.8 DID. Among the 47 prefectures, decreasing trends were observed in 34, while in the remaining 13 prefectures increasing trends were recorded. In 2016, no significant differences in the mean usage of oral cephalosporins among the three regions were observed. The mean usage of oral macrolides in the eastern (4.1 DID) was significantly lower than that in the central region (4.7 DID) (p = 0.009) and the western (4.8 DID) (p = 0.002). The mean usage of oral quinolones in the western (3.2 DID) was significantly higher than that in the eastern (2.3 DID) (p ＜ 0.001) and central (2.7 DID) (p = 0.001) regions. To determine appropriate targets for the implementation of antimicrobial stewardship for reducting the use of broad-spectrum oral antimicrobials, further studies are required to identify the reasons underlying these differences.