Medical cannabis legalization and opioid prescriptions: evidence on US Medicaid enrollees during 1993-2014.

BACKGROUND AND AIMS: While the United States has been experiencing an opioid epidemic, 29 states and Washington DC have legalized cannabis for medical use. This study examined whether state-wide medical cannabis legalization was associated with reduction in opioids received by Medicaid enrollees.

DESIGN: Secondary data analysis of state-level opioid prescription records from 1993-2014 Medicaid State Drug Utilization Data. Linear time-series regressions assessed the associations between medical cannabis legalization and opioid prescriptions, controlling for state-level time-varying policy covariates (such as prescription drug monitoring programs) and socio-economic covariates (such as income).

SETTING: United States.

PARTICIPANTS: Drug prescription records for patients enrolled in fee-for-service Medicaid programs that primarily provide health-care coverage to low-income and disabled people.

MEASUREMENTS: The primary outcomes were population-adjusted number, dosage and Medicaid spending on opioid prescriptions. Outcomes for Schedule II opioids (e.g. hydrocodone, oxycodone) and Schedule III opioids (e.g. codeine) were analyzed separately. The primary policy variable of interest was the implementation of state-wide medical cannabis legalization.

FINDINGS: For Schedule III opioid prescriptions, medical cannabis legalization was associated with a 29.6% (P = 0.03) reduction in number of prescriptions, 29.9% (P = 0.02) reduction in dosage and 28.8% (P = 0.04) reduction in related Medicaid spending. No evidence was found to support the associations between medical cannabis legalization and Schedule II opioid prescriptions. Permitting medical cannabis dispensaries was not associated with Schedule II or Schedule III opioid prescriptions after controlling for medical cannabis legalization. It was estimated that, if all the states had legalized medical cannabis by 2014, Medicaid annual spending on opioid prescriptions would be reduced by 17.8 million dollars.

CONCLUSION: State-wide medical cannabis legalization appears to have been associated with reductions in both prescriptions and dosages of Schedule III (but not Schedule II) opioids received by Medicaid enrollees in the United States.