Effectiveness of drug safety measures for reducing the incidence of adverse drug reactions: Post-hoc analysis of data from all-case surveillance of iguratimod using generalized estimating equations

Abstract

A post-marketing study was performed on all patients who had started treatment with iguratimod, a conventional synthetic disease-modifying antirheumatic drug approved in Japan. During the study period, various safety measures were implemented to reduce risks. We investigated the frequency of adverse drug reactions before and after implementation of each safety measure to examine the preventive effect of these measures. Post-hoc analysis was performed using data from all-case surveillance of iguratimod. The subjects were all of the patients receiving iguratimod for whom safety information was obtained. To identify the time after starting administration when adverse drug reactions were most likely to occur, a generalized linear mixed-effect model was applied for the period from initiation of administration until occurrence of reactions in each patient. The mean incidence of adverse drug reactions per patient was compared before and after the implementation of safety measures by using generalized estimating equations based on a two-sided test, 95% confidence interval, and 5% significance level. The number of patients treated with iguratimod was not related to changes in the number of patients with adverse drug reactions. After implementing precautions regarding co-administration with warfarin and liver dysfunction, the estimated mean incidence rate of adverse drug reactions (95% confidence interval) decreased significantly to 0.73 (0.59-0.90) and 0.72 (0.55-0.94), respectively. Accordingly, some of the implementation of safety measures significantly reduced adverse drug reactions. The effectiveness of safety measures implemented during the all-case surveillance of iguratimod was evaluated, revealing that early implementation of safety measures decreased the incidence of adverse drug reactions.