Exposure to Potential CYP450 Pharmacokinetic Drug-Drug Interactions among Osteoarthritis Patients: Incremental Risk of Multiple Prescriptions

Patients taking more than one drug metabolized through the cytochrome P450 (CYP450) enzyme system experience a drug–drug exposure (DDE), which puts them at risk for a potential pharmacokinetic drug–drug interaction (DDI), defined as two or more drugs interacting in such a way that the effectiveness and/or toxicity of one or all drugs are changed. Any patient subjected to a DDE is at risk for a potentially serious DDI, the epidemiology of which has not been thoroughly studied. Many drugs are metabolized primarily via the CYP450 enzyme system, including certain opioids used to manage moderate to severe chronic pain. We conducted a retrospective analysis of a large commercial claims database and a Medicare database to assess the prevalence of DDEs among patients with osteoarthritis taking CYP450‐metabolized opioids. The overall prevalence of DDEs in this population was 26%, with females more likely to experience DDEs than males (28.4% vs. 21.0%, respectively). The number of unique concurrent prescriptions at baseline, gender, age, and Charlson Comorbidity Index were statistically significant predictors of DDEs (P