Many insurers are using formulary design to influence opioid prescribing, but it is unclear if these changes lead to reduced use or just substitution between opioids. We evaluated the effect of a new prior authorization process implemented in July 2015 for extended-release (ER) oxycodone by Blue Shield of California. Compared to other commercially insured Californians, among 880,000 Blue Shield enrollees, there was a 36 percent drop in monthly rates of ER opioid initiation relative to control-group members, driven entirely by decreases in ER oxycodone initiation and without any substitution toward other ER opioids. This reduction was offset by a 1.4 percent relative increase in the rate of short-acting opioid fills. There was no significant change in the overall use of any opioids prescribed, measured as morphine milligram equivalents. This suggests that though insurers can play a meaningful role in reducing the prescribing of high-risk ER opioids, a formulary change focused on ER opioids alone is insufficient to decrease total opioid prescribing.
Keywords: Managed Care - Quality < Managed Care; Pharmaceuticals; Public Health.