OBJECTIVES : Gabapentin is increasingly receiving attention for purported off-label uses, but has just two FDA-approved indications. In December 2019, the FDA issued a warning regarding risks associated with concomitant use of gabapentin with central nervous system depressants (CNS-D). This study examined historical gabapentin off-label utilization and identified concomitant CNS-D prescription drug use.

METHODS : This cross-sectional study used National Ambulatory Medical Care Survey data from 2011-2015. Gabapentin utilization was determined by outpatient visits with a gabapentin prescription listed for adults (≥18 years), aggregated across years. ICD-9-CM diagnosis codes in any position identified FDA-approved indications, partial onset seizures or postherpetic neuralgia. Single-level Clinical Classifications Software (CCS) diagnosis categories were used to identify off-label uses. CNS-D drug classes examined were opioids, benzodiazepines, hypnotics, skeletal muscle relaxants, first generation antihistamines, sedating antidepressants, and atypical antipsychotics. Concomitance was defined as ≥1 order for any CNS-D medication at a gabapentin visit.

RESULTS : Among 236,117 outpatient visits from 2011-2015, n=5,379 (2.3%) visits documented current or new gabapentin prescriptions. Only 53 (0.99%) of gabapentin visits were for FDA-approved indications. The most frequent off-label CCS diagnoses for visits across all years were: spondylosis, intervertebral disc disorders, or other back problems (26.5%), other nervous system disorders (16.9%), and other connective tissues disease (10.7%). Overall, 55.3% of visits with gabapentin prescriptions had ≥1 concomitant CNS-D prescription recorded at the same visit, most frequently; antidepressants (23.9%), opioids (22.9%), and benzodiazepines (17.2%).

CONCLUSIONS : In this nationally representative sample, outpatient gabapentin utilization was <1% for FDA-approved indications. The most frequent off-label uses identified suggest that gabapentin is widely employed in the treatment of neuropathic and musculoskeletal pain, consistent with previous literature. The high proportions of concomitant CNS-D usage suggest that future utilization studies should examine the effect of the recent FDA warning, and implicate the urgent need for research on off-label gabapentin uses.