Early effects of scheduling gabapentin on medication adherence among epilepsy patients on gabapentin in Virginia.

BACKGROUND

Due to concerns about misuse and diversion, eight states have scheduled gabapentin as a controlled substance. The effect of this change on patient adherence is unknown.

OBJECTIVES

To estimate the effect of Virginia's scheduling of gabapentin on medication adherence among epilepsy patients.

RESEARCH

DESIGN

Using all-payer claims data from Virginia and Colorado for 2017-2019, we identified patients with focal seizures who had a claim for gabapentin, pregabalin, or levetiracetam. The primary outcome was proportion of days covered over six-month periods. Effects were estimated using a triple-difference approach comparing patients 1) pre- vs. post-policy, 2) in Virginia vs. Colorado, and 3) on gabapentin vs a comparison medication. Analyses were repeated excluding patients with opioid claims.

RESULTS

Gabapentin scheduling in Virginia was associated with a 3.6 (SD: 1.1, p-value <0.001) percentage point decrease in proportion of days covered. The share of epilepsy patients with ≥80% of days covered decreased from 67.5% to 60.2% (adjusted difference: -7.5%, SD: 2.2, p-value <0.001). The proportion of gabapentin patients with a concurrent opioid prescription did not significantly change and excluding these patients had minimal effect.

CONCLUSIONS

In the six months following Virginia's policy change, scheduling gabapentin was associated with a decline in the proportion of days covered among epilepsy patients. Given ongoing state-level gabapentin policy changes, continued research on the impacts of scheduling gabapentin on patient care and barriers to medication access is warranted.