Background: The comparative safety of serotonin and norepinephrine reuptake inhibitors (SNRIs) as adjuvants to short-acting opioids in older adults is unknown even though SNRIs are commonly used. We compared the effects of SNRIs versus nonsteroidal anti-Inflammatory drugs (NSAIDs) on delirium among nursing home residents when SNRIs or NSAIDs were added to stable regimens of short-acting opioids.

Methods: Using 2011-2016 national Minimum Data Set (MDS) 3.0 and Medicare claims data to implement a new-user design, we identified a cohort of nursing home residents receiving short-acting opioids who initiated either an SNRI or an NSAID. Delirium was defined from the Confusion Assessment Method in MDS 3.0 assessments and ICD9/10 codes using Medicare hospitalization claims. Propensity score matching balanced underlying differences for initiating treatments on 39 demographic and clinical characteristics (nSNRIs = 5350; nNSAIDs = 5350). Fine and Gray models provided hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for the competing risk of death.

Results: Hydrocodone was the most commonly used short-acting opioid (48%). Residents received ~23 mg daily oral morphine equivalent at the time of SNRIs/NSAIDs initiation. The majority were women, non-Hispanic White, and aged ≥75 years. There were no differences in any of the confounders after propensity matching. Over 1 year, 10.8% of SNRIs initiators and 8.9% of NSAIDs initiators developed delirium. The rate of delirium onset was similar in SNRIs and NSAID initiators (HR(delirium in nursing home or hospitalization for delirium):1.10; 95% CI: 0.97-1.24; HR(hospitalization for delirium): 1.06; 95% CI: 0.89-1.25), and were similar regardless of baseline opioid daily dosage.

Conclusions: Among nursing home residents, adding SNRIs to short-acting opioids does not appear to increase risk of delirium relative to initiating NSAIDs. Understanding the comparative safety of pain regimens is needed to inform clinical decisions in a medically complex population often excluded from clinical research.