To explore the clinical application and long-term safety of hydroxychloroquine sulfate (HCQ) in the treatment of rheumatic diseases.

A multi-center cross-sectional study was conducted between August 2017 and August 2018 in a random sample of eleven medical institutions of rheumatology and immunology in China. Patients who took HCQ for more than 3 months were enrolled into this study. The cumulative dose and long-term side effects of HCQ were recorded. The changes of laboratory indexes before and after treatment with HCQ were analyzed. Categorical variables were presented with counts and proportions, and evaluated by Chi-square test. Continuous parametric data were presented as Mean±standard deviation, and evaluated by Student'st test or Mann-Whitney U test. P-values less than 0.05 were considered statistically significant.

A total of 886 patients with rheumatic diseases were enrolled into this study, including 505 cases with systemic lupus erythematosus (57.0%), 210 cases with rheumatoid arthritis (23.7%), 80 cases with Sjögren's syndrome (9.0%), 57 cases with undifferentiated connective tissue disease (6.4%), 12 cases of systemic vasculitis (1.4%), 10 cases of mixed connective tissue disease (1.1%), 7 cases of myositis (0.8%) and 5 cases with systemic sclerosis (0.6%). The most common long-term side effects of HCQ was skin or mucous lesions (12.4%) and vision problems (8.0%). Other adverse reactions included problems of digestive system (3.0%), nervous system (2.1%), musculoskeletal system (1.1%) and cardiovascular system (0.9%). 140 cases (15.8%) had stopped taking HCQ during the treatment. More than half of them decided to stop taking medicine by themselves. Fifty-four patients (6.1%) stopped using HCQ due to side effects while 24 of them took it again, and another 12 patients (1.4%) stopped the drug due to remission of illness. Patients were divided into three groups according to the cumulative dose of HCQ: less than 500 g, 500-1 000 g and more than 1 000 g respectively. There was significant difference in the incidence of long-term side effects among the three groups (χ²=6.382, P=0.041). The last group (more than 1 000 g) suffered the highest incidence of long-term adverse reactions (37.1%). No severe adverse drug reactions were observed in this study.

Hydroxychloroquine is widely used in the treatment of rheumatic diseases. The incidence of long-term side effects is 20.4%, is 6.1% lead to drug withdrawal, which are especially related to the cumulative doses. It should be adjusted properly according to the clinical application.

Rheumatic disease; Patient safety; Hydroxychloroquine; Clinical application