5A-04 - Changes in Gabapentin Prescription Fills Among Medicaid Enrollees Following State-Level Schedule V Controlled Substance Classification

Background: Despite limited on-label indications, gabapentin prescriptions have steadily increased in the United States since the late 2000s. Driven by concerns of misuse and increasing detection in fatal overdoses, Kentucky (KY) and West Virginia (WV) became the first states to classify gabapentin as a schedule V controlled substance in July 2017 and June 2018, respectively. Given recent gabapentin policy considerations nationally, it is imperative to understand the impacts of KY’s and WV’s implementations.

Objectives: To assess the impact of gabapentin’s schedule V controlled substance classification in KY and WV on total outpatient gabapentin prescriptions paid for by Medicaid programs.

Methods: Using a controlled interrupted time series design, we calculated the immediate and trend changes of outpatient gabapentin prescriptions among Medicaid enrollees in two states (KY, WV), separately. Data from North Carolina (NC) was used as a control to account for secular changes given the lack of controlled substance designation in NC during the study period. Total prescriptions per quarter (Q) were calculated using Medicaid’s State Drug Utilization Data, and rates were established using state-specific Medicaid and CHIP average enrollment. Analyses were confined between Q1 2016 and Q4 2019 to eliminate the potential influence of the COVID-19 pandemic and its associated healthcare disruptions. We used generalized linear models adjusting for autocorrelation to estimate the trends before and after each state’s policy implementation (Interruptions modeled at Q3 2017 in KY and Q3 2018 in WV).

Results: Overall, utilization rates of gabapentin were higher in KY and WV relative to NC throughout the study period. After the policy change in KY, there was a sustained decrease in the trend of quarterly prescribing relative to NC (-11.0 prescriptions per 1,000 enrollees per Q [95%CI: -13.3, -8.6]). Though not statistically significant, an immediate decrease in prescription rate was also observed (-5.1 prescriptions per 1,000 enrollees [95%CI: -14.3, 4.0]). In WV, in the month following the policy, there were both an immediate decrease in prescribing (-19.0 prescriptions per 1,000 enrollees [95%CI: -32.6, -5.3]) and a sustained decrease in trend observed relative to NC (-3.7 prescriptions per 1,000 enrollees per Q [95%CI: -7.0, -0.5]).

Conclusions: The decrease in trend of gabapentin prescriptions observed in both KY and WV following the schedule V classification indicates that one desired impact of the policy (i.e., overall decreased prescribing) was achieved among the Medicaid population. Importantly, the policy’s effects on other populations and potential unintended effects were not addressed in this study.