Drug-drug Interactions in Nursing Home Residents: Analysis from the COME-ON Trial

Background: as a result of the high prevalence of polypharmacy in nursing homes (NHs), nursing home residents (NHRs) are exposed to numerous drug-drug interactions (DDIs) that can lead to adverse drug effects, and increased morbidity and mortality.

Objectives: to evaluate (i) the prevalence of DDIs among NHRs and its evolution over time, and (ii) factors associated with a favourable evolution.

Design: posthoc analysis of the COME-ON study, a cluster-randomised controlled trial aiming at reducing potentially inappropriate prescriptions in NHs, through the implementation of a complex intervention.

Setting And Subjects: 901 NHRs from 54 Belgian NHs.

Methods: DDIs were identified using a validated list of 66 potentially clinically relevant DDIs in older adults. We defined a favourable evolution at 15 months as the resolution of at least one DDI present at baseline, without the introduction of any new DDI. Factors associated with a favourable evolution were analysed using multivariable logistic regression.

Results: at baseline, 475 NHRs (52.7%) were exposed to at least 1 DDI and 225 NHRs (25.0%) to more than one DDI. Most common DDI was 'Concomitant use of at least three central nervous system active drugs'. At 15 months, we observed a 6.3% absolute decrease in DDI prevalence in intervention group, and a 1.0% absolute increase in control group. The intervention, older age and private NH ownership were significantly associated with a favourable DDI evolution.

Conclusion: a high prevalence of DDI in Belgian NHs was observed, but the COME-ON intervention was associated with a favourable evolution over time.