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

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.

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

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.

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.

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.