Impact of state-level gabapentin schedule V controlled substance classification on utilization and fatal overdose

PROJECT ABSTRACT Polysubstance-involved overdose rates have risen across the United States. Gabapentin, an anticonvulsive medication with FDA-approved uses for postherpetic neuralgia and partial seizures, is a co-substance of growing concern. Despite its limited on-label indications, gabapentin prescriptions have steadily increased, likely driven by off-label use. Reports of recreational abuse and misuse, particularly among individuals with opioid use disorder, are of particular concern, given that concurrent gabapentin and opioid misuse may result in death. Gabapentin has been increasingly detected in fatal overdose toxicology, especially in the Southeast United States. These harms have led to calls for increased monitoring or scheduling of gabapentin. In June 2018, West Virginia (WV) became the second of eight states to classify gabapentin as a schedule V controlled substance; however, the net effectiveness of the policy is unknown. Policy changes concerning controlled substances, which often result in altered prescribing patterns, have the potential to address concerns like over-prescribing and misuse but may also endanger users with dependence. Limiting access to prescribed medications may result in a shift to alternative substances obtained from nonmedical sources with unknown potency and potentially high levels of contaminants. This study will utilize a controlled interrupted time series design to assess the impact of the policy in WV, using North Carolina (NC) as a control state to account for secular changes given the lack of controlled substance designation in that state. Using WV’s Forensic Drug Database and NC’s State Unintentional Drug Overdose Reporting System, Aim 1 will assess whether gabapentin’s schedule V controlled substance classification in WV was associated with a change in 1A) the rate of gabapentin involved fatal overdoses, and 1B) the overall fatal overdose rate. Using Merative MarketScan Commercial Claims and Encounters Databases, Aim 2 will assess whether gabapentin’s schedule V classification in WV was associated with a change in prescription utilization among 2A) all privately-insured adults and 2B) adults with diabetic neuropathy for whom gabapentin is clinically indicated. Using Medicaid’s State Drug Utilization Data, Aim 3 will assess whether gabapentin’s schedule V classification in WV was associated with a change in outpatient gabapentin prescriptions paid for by Medicaid. Our longitudinal data analysis approach will allow us to identify both immediate effects and trend changes resulting from the scheduling policy’s implementation. As more states, as well as national policymakers, consider classifying gabapentin as a schedule V controlled substance, it is imperative to understand the impacts of WV’s implementation, both intended and potentially unintended. Results from this study will enhance the evidence base of gabapentin’s schedule V classification and inform future policy discussions.