Prevalence and Duration of Potential Drug-Drug Interactions Among US Nursing Home Residents, 2018-2020.

Background: Nursing home (NH) residents are at increased risk of drug-drug interactions (DDIs) due to multimorbidity and polypharmacy. While prior research suggests that many DDIs lead to adverse drug events in older adults, the extent of exposure to potentially clinically relevant DDIs among United States (US) NH residents is largely unknown.

Methods: In this cohort study, we calculated the prevalence and duration of exposure to 98 potential DDIs among US NH residents from 2018 to 2020. DDIs were sourced from three expert consensus publications, some of which defined similar interactions and overlapping drug combinations, allowing comparisons within and across lists. Data were drawn from Medicare claims linked to Minimum Data Set 3.0 clinical assessments. Eligible residents included Medicare Fee-for-Service beneficiaries aged ≥ 66 years living in NHs with observable Part D prescription drug data. DDI exposure was defined as ≥ 1 day of concurrent use of orally administered medications. Prevalence was calculated as the proportion of residents exposed to each DDI; duration was measured as the median number of days residents concurrently used the medications of interest.

Results: Among 485,251 NH residents, 61.6% experienced ≥ 1 potential DDI over 272,780 person-years. The 12 most prevalent DDIs involved central nervous system (CNS)-active drugs, anticholinergics, antihypertensives, opioids, and diuretics. Of these DDIs, concurrent use of acetylcholinesterase inhibitors and heart rate-reducing drugs had the longest median exposure duration (81 days; Q1-Q3, 24-235). The most prevalent DDI, concomitant use of ≥ 3 CNS-active drugs, was observed in 27.1% (95% CLs, 27.0%, 27.2%) of residents.

Conclusions: Nearly two-thirds of NH residents were exposed to medication combinations linked to potential DDIs, although the prevalence and duration of exposure associated with individual DDIs varied. Future research should determine which DDIs are most clinically significant and investigate barriers to reducing exposure duration in this high-risk population.