Development of medication regimen complexity index: Japanese version and application in elderly patients

Background Medication regimen complexity includes various aspects of a regimen, including the dosage form, number of medications and need for additional information for use. Complicated medication regimens cause non-adherence to prescribed medications, making it essential to evaluate medication regimen complexity in older adults to improve adherence to prescribed medications and clinical outcomes. The medication regimen complexity index is currently the most widely used scale for quantifying regimen complexity; however, it has yet to be adopted in Japan. Objective This study aimed to translate the medication regimen complexity index to Japanese and assess its reliability and validity for application in elderly patients in Japan. Setting This study was conducted in a clinic that provides home medical care to patients in the southern part of Ibaraki prefecture, Japan. Method The validation process consisted of translation of the original English version of the medication regimen complexity index to Japanese followed by back-translation to English, comparison of the back-translated and original versions, pilot testing, and assessment of the Japanese version by two raters using the medication regimens of 72 patients with chronic diseases. Main outcome measure The psychometric properties of the index were evaluated according to inter-rater and test-retest reliability, and convergent and discriminant validity. Results The mean age of the 72 patients was 84.3 years. The scale showed high inter-rater reliability (intraclass correlation coefficient 0.946) and test-retest reliability (intraclass correlation coefficient 0.991) for total scores. The number of medications was positively correlated with total medication regimen complexity index score (r_s = 0.930, P < 0.001). There were no statistically significant differences between age, sex and Charlson Comorbidity Index and medication regimen complexity index score (P > 0.05). Conclusions The Japanese version of the medication regimen complexity index is a reliable and valid tool for assessing the complexity of medication regimen in Japanese elderly patients.