Using a retrospective database analysis, OA patients taking at least one CYP450-metabolized opioid (codeine, fentanyl, hydrocodone, methadone, oxycodone, or tramadol) and at least one other prescription drug metabolized via the CYP450 system were evaluated for an incident drug-drug exposure (DDE), which places them at risk for experiencing a pharmacokinetic drug-drug interaction (DDI).