Assessing the Risk for Falls in Older Adults After Initiating Gabapentin Versus Duloxetine

Abstract

Background: The evidence informing the harms of gabapentin use are at risk of bias from comparing users with nonusers.

Objective: To describe the risk for fall-related outcomes in older adults starting treatment with gabapentin versus duloxetine.

Design: New user, active comparator study using a target trial emulation framework.

Setting: MarketScan (IBM) commercial claims between January 2014 and December 2021.

Participants: Adults aged 65 years or older with diabetic neuropathy, postherpetic neuralgia, or fibromyalgia and without depression, anxiety, seizures, or cancer in the 365 days before cohort entry.

Intervention: New initiation of treatment with gabapentin or duloxetine (comparator).

Measurements: The primary outcome was the hazard of experiencing any fall-related visit in the 6 months after initiating gabapentin or duloxetine until discontinuation of treatment. Secondary outcomes were hazard of severe fall-related events defined as a fall associated with hip fracture or emergency department visit or hospitalization associated with a fall. Stabilized inverse probability of treatment weighting was used to adjust for baseline characteristics.

Results: Our analytic cohort included 57 086 older adults with a diagnosis of interest initiating treatment with gabapentin (n = 52 152) or duloxetine (n = 4934). Overall median follow-up duration was 30 days (IQR, 30 to 90 days). Weighted cumulative incidence of a fall-related visit per 1000 person-years at 30, 90, and 180 days was 103.60, 90.44, and 84.44 for gabapentin users and 203.43, 177.73, and 158.21 for duloxetine users, respectively. At 6-month follow-up, incident gabapentin users had lower hazard of falls (hazard ratio, 0.52 [95% CI, 0.43 to 0.64]), but there was no difference in the hazards of experiencing severe falls. Results were similar across sensitivity and subgroup analyses.

Limitation: Claims may contain fewer frail adults and undercount falls.

Conclusion: Compared with incident use of duloxetine, incident use of gabapentin was not associated with increased fall-related visits.

Primary funding source: None.