Cohort study of new off-label gabapentin prescribing in chronic opioid users

Gabapentin is commonly prescribed as an off-label adjunct to opioids because of its safer risk profile. Recent evidence has shown an increased risk of mortality when coprescribed with opioids. Therefore, we aimed to evaluate whether the addition of off-label gabapentin in patients with chronic opioid use is associated with a reduction in opioid dosage.

We performed a retrospective cohort study of patients with chronic opioid use with a new off-label gabapentin prescription (2010-2019). Our primary outcome of interest was a reduction in opioid dosage measured via oral morphine equivalents (OME) per day after the addition of a new off-label gabapentin prescription.

In our cohort of 172,607 patients, a new off-label gabapentin prescription was associated with a decrease in opioid dosage in 67,016 patients (38.8%) (median OME/day reduction:13.8), with no change in opioid dosage in 24,468 patients (14.2%), and an increase in opioid dosage in 81,123 patients (47.0%) (median OME/day increase: 14.3). A history of substance/alcohol use disorders was associated with a decrease in opioid dosage after the addition of a new off-label gabapentin (aOR 1.20, 95% CI 1.16 to 1.23). A history of pain disorders was associated with a decrease in opioid dosage after the initiation of a new gabapentin prescription including arthritis (aOR 1.12, 95% CI 1.09 to 1.15), back pain (aOR 1.10, 95% CI 1.07 to 1.12), and other pain conditions (aOR 1.08, 95% CI 1.06 to 1.10).

In this study of patients with chronic opioid use, an off-label gabapentin prescription did not reduce opioid dosage in the majority of patients. The coprescribing of these medications should be critically evaluated to ensure optimal patient safety.