Background Hydroxychloroquine (HCQ) has been widely used in the world. However, due to the problem of retinopathy caused by chloroquine, it had not been approved in Japan until 2015, although it has been used for limited number of patients in some institutions. The primary purpose of our study is to collect the data on adverse effect of HCQ among Japanese patients with systemic lupus erythematosus. We also assessed the efficacy of our methods to improve the tolerability in cases with gastrointestinal and dermatological side effects of HCQ.

Method We retrospectively collected the data of all the 174 lupus patients treated with HCQ from the electric medical record of St Luke’s International Hospital, Tokyo, Japan. We extracted the following parameters during the period between April 2008 and June 2017; patients’ baseline characteristics, side effects and duration of using HCQ, and reasons of discontinuation. As for dermatological side effects, some of the patients underwent oral desensitisation; HCQ was once stopped, and after confirming negative DLST and obtaining consent from patients, it was resumed with the 36 days-desensitisation protocol. For patients with gastrointestinal side effects, some of the patients were prescribed Hangeshashinto, a traditional herbal medicine for gastrointestinal discomfort, in addition to HCQ.

Result During the period, the mean age of the patients was 41.8. 161 patients (92.5%) were female and 152 patients (87.4%) were treated with steroids. The average duration of using HCQ was 582.4 days. 21 patients (12.0%) had side effects and 14 patients (8.0%) discontinued HCQ. 10 patients had skin side effects, 7 were performed DLST, 7 were negative, and 2 resumed HCQ. 5 patients had gastrointestinal side effects, 2 were prescribed Hangeshashinto. 2 patients were possible retinopathy and stopped HCQ.

Conclusion This is one of the largest studies which reported well tolerability of HCQ in Japanese real world practice. Despite the concern of retinopathy, there were only 2 cases who stopped HCQ due to possible retinopathy in this study. In addition, our methods may help continuing HCQ in patients with skin or gastrointestinal side effects. Further larger study is needed to confirm these results.