Use of multiple pharmacies can predict opioid overdosing

In many states, Medicaid programs monitor the number of pharmacies visited to determine risk for misuse or abuse of opioid medications. Pharmacy shopping can be a way to obtain more opioid prescription drugs than medically necessary.

Despite knowing that using multiple pharmacies is linked with drug misuse, there is no consensus regarding the threshold number of pharmacies or specified length of time that can define pharmacy-shopping behavior. Further, there is a risk that relying on pharmacy shopping as an indicator of opioid misuse could misidentify patients who legitimately have used multiple pharmacies due to insurance coverage changes, moving, traveling and vacations.

For the study, a multicenter team of researchers examined records of more than 90,000 Medicaid enrollees who used three or more opioid prescriptions for 90 days in 2008 through 2010. The study population was limited to a cohort of Medicaid enrollees ages 18 to 64 who were long-term opioid users.

Results of the analysis showed that within a 90-day interval a threshold of four pharmacies had the highest diagnostic odds ratios for opioid overdose events, and could be considered as an indicator for pharmacy shopping. Further, the overdose rate was higher within a subgroup with overlapping prescriptions.

The authors recommended that for patients whose use of overlapping prescriptions and multiple pharmacies cannot be justified medically, patient review and restriction programs (PRRs) could restrict reimbursement for controlled prescription drugs to a single designated physician and one pharmacy.