3F-01 - Epidemiology of the Gabapentinoid-Loop Diuretic Prescribing Cascade among US Nursing Home Residents

Background: Prescribing cascades occur when an adverse effect of one medication is treated with another medication, contributing to unnecessary polypharmacy. Gabapentinoids (gabapentin and pregabalin) are commonly used in nursing home residents and can cause edema, triggering a loop diuretic prescribing cascade. The epidemiology of the gabapentinoid-loop diuretic prescribing cascade in US nursing home residents is not well described.

Objectives: To estimate the 90-day incidence and risk factors for loop diuretic initiation after starting a gabapentinoid in long-term nursing home residents.

Methods: We included US Medicare beneficiaries who were long-term nursing home residents and initiated a gabapentinoid between 03/30/2016 and 9/30/2020. The date of the first gabapentinoid dispensing was the index date. We excluded those without 12 months of continuous enrollment in Medicare Fee-for-Service with Part D (prescription drug coverage) or were aged < 66 years at the index date, as well as those without a Minimum Dataset clinical assessment (MDS) within 120 days before the index date. We then excluded those who had a diagnosis code for renal disease or heart failure or a claim for a gabapentinoid or loop diuretic in the 180 days prior to the index date. We followed patients until a loop diuretic dispensing (outcome) or censoring (day 90 of follow-up, death, Medicare disenrollment, or 7 consecutive days without gabapentin use). We measured covariates in the 180 days prior to index. We defined a higher gabapentinoid daily dose as >600 mg gabapentin or >150 mg pregabalin. Using multivariable Poisson regression models, we estimated adjusted risk ratios (aRR) with 95% robust confidence intervals to identify risk factors.

Results: We identified 23,544 eligible residents (mean age 82.3 [SD=8.49] years; 72% female; 85% non-Hispanic White; 9.2% Black; 94.8% initiating gabapentin). Of these, 994 (4.2%) had a loop diuretic dispensing during follow-up. Risk was higher with age 86-90 years (aRR=1.60) or ≥91 years (aRR=1.38); a diagnosis of chronic pain or fibromyalgia (aRR=1.16), or diabetes (aRR=1.23); and receipt of potassium-sparing diuretics (aRR=1.53), thiazide diuretics (aRR=1.27), or 15 or more unique medications (aRR=1.18). Higher (versus lower) weekly gabapentin dose was associated with a 1.45 times higher prescribing cascade risk over 13 weeks.

Conclusions: Approximately one in twenty NH residents who initiates gabapentinoids receives a potentially unnecessary loop diuretic within three months. Higher gabapentinoid dose and medication burden were associated with increased risk. Future studies should examine the causal effects of this prescribing cascade on clinical outcomes.