The purpose of this study is to explore the associations between polypharmacy and multimorbidity using conventional and novel measures of polypharmacy. In this cross-sectional study, data on fee-for-service (FFS) Medicaid enrollees with at least 1 chronic condition and aged 18–64 years (N = 38,329) were derived from the 2010 Medicaid Analytic eXtract (MAX) files of Maryland and West Virginia. Polypharmacy, by the authors\u27 novel definition, was determined as simultaneous use of ≥5 drugs for a consecutive period of 60 days. Multimorbidity was defined as having ≥2 chronic conditions based on the US Department of Health and Human Services framework. The association between multimorbidity and polypharmacy was examined with chi-square tests and logistic regression. Polypharmacy prevalence was estimated at 50.9% using the novel definition, as compared to 16.7% and 64.9% for the 2 commonly used conventional measures, respectively. For all 3 definitions, individuals with multimorbidity were more likely to have polypharmacy than those without multimorbidity (P \u3c 0.001). The authors also consistently found, using all definitions, that those who were older, female, white, and eligible for Medicaid because of cash assistance were more likely to have polypharmacy (all P \u3c 0.001). Polypharmacy was highly prevalent and significantly associated with multimorbidity among Medicaid FFS enrollees irrespective of the definitions used. The new measure may provide a more comprehensive and accurate estimation of polypharmacy than the conventional measures. These findings suggest the need for a paradigm shift from disease-specific care to patient-centered collaborative care to manage patients with multimorbidity and polypharmacy
