Educational effects of a workshop on quantitative drug–drug interaction assessment for pharmacists: a pre–post study

Background Drug–drug interactions (DDIs) are a major cause of adverse drug events and require appropriate evaluation and management in clinical practice. Quantitative evaluation methods based on pharmacokinetic parameters have been proposed to assess the clinical significance of DDIs. The Pharmacokinetic Drug Interaction Significance Classification System (PISCS) provides a framework for estimating changes in drug exposure using the contribution ratio and inhibition ratio; however, opportunities for pharmacists to learn its practical application remain limited. This study aimed to evaluate the educational effects of a workshop on DDI management using quantitative evaluation methods. Methods Workshops were conducted at two national pharmaceutical conferences in Japan. A total of 45 participants were included in the analysis. Participants completed questionnaires before and after the workshop. Self-efficacy in DDI management was assessed using a five-point Likert scale. Results Although 60.0% of participants reported being aware of the PISCS, 55.6% had never used it in clinical practice. Self-efficacy significantly improved in all evaluated domains after the workshop, including confidence in obtaining DDI information, quantitatively predicting drug exposure changes, and making prescription proposals based on DDI evaluation (all p < 0.001). Furthermore, 95.6% of participants considered the workshop useful for clinical practice, and 91.1% reported that they felt able to apply the PISCS in prescription review and consultation. Conclusions These findings suggest that a case-based workshop on quantitative DDI assessment may improve pharmacists’ confidence in DDI management and facilitate the practical application of the PISCS in clinical settings.