Are prescription drug monitoring laws effective for all? Evidence from administrative data

States have responded to the opioid epidemic by implementing statewide prescription drug monitoring programs (PDMPs). By helping identify patients at "high risk" for suspected misuse, diversion, and doctor shopping, mandatory PDMPs aim to reduce prescription-opioid misuse and related overdose mortality. So far, however, there is little research on whether prescribing declines following mandatory PDMP laws were targeted toward patient-age groups with a higher incidence of prescription-opioid misuse. To examine the heterogeneous impacts of state laws on different patient-age groups, this study exploits the implementation of PDMP reforms in Kentucky starting July 20, 2012. The analysis uses novel data from PDMPs, including the universe of opioid prescriptions dispensed between January 2012 and November 2013. Individual prescriber-level difference-in-differences, with Indiana as the control state, show that practitioners responded to Kentucky's new laws as expected, by prescribing opioids to fewer patients and authorizing fewer prescriptions and days of supply per prescription. Opioid prescribing declined most sharply to patient sub-populations with the highest past incidence of prescription-opioid-involved overdose mortality-ages 25-54 years. Considering the implication for overdose mortality, we find that Kentucky's PDMP reform was associated with significant declines in prescription-opioid overdose deaths, particularly among adolescents and younger adults (ages 15-34 years). However, the decline in prescription-opioid-involved mortality was offset by an increase in illicit-drug mortality, resulting in no net change in total drug-overdose mortality in Kentucky following its mandatory PDMP.