Findings from a cross-sectional study show that drug interactions are common among community-dwelling older adults and are related to the number of medications and hospitalization in the previous year. The study has been published in the Journal of Clinical Pharmacy and Therapeutics.

J.T. Hanlon, PharmD, MS, and colleagues set out to examine the prevalence of possible drug-drug and drug-disease interactions and associated variables in older adults. The study (n=3,055) included adults aged 70–79 years without mobility limitations at their baseline visit in the Health Aging and Body Composition Study. Main outcomes were potential drug-drug and drug-disease interactions according to established criteria applied to self-reported prescription and non-prescription drug use.  

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The findings showed over 1/3 of patients (34.1%) had ≥1 interaction and about 1/4 had ≥1 drug-drug interaction. Close to 10.7% of patients had a drug-drug interaction involving a non-prescription drug. Potential drug-disease interactions were seen in 16% of patients with 37% having one involving non-prescription drugs.

The most common drug-drug interaction was between non-steroidal anti-inflammatory (NSAIDs) and antihypertensives. The most common drug-disease interaction was aspirin/NSAID use in patients with a history peptic ulcer disease without gastroprotection. 

Each prescription drug raised the likelihood of having ≥1 type of drug interaction by 35–40% (drug-drug interaction adjusted odds ratio [AOR] 1.35, 95% CI: 1.27–1.42; drug-disease interaction AOR 1.30; 95% CI: 1.21–1·40; both AOR 1.45; 95% CI: 1.34–1.57]. 

In addition, having a prior hospitalization raised the likelihood of having  ≥1 type of drug interaction by 49–84% vs. patients not hospitalized (drug-drug interaction AOR 1.49, 95% CI: 1.11–2.01; drug-disease interaction AOR 1.69, 95% CI: 1.15–2.49; both AOR 1.84, 95% CI: 1.20–2.84).

Dr. Hanlon concluded, “Longitudinal studies are needed to evaluate the impact of drug interactions on health-related outcomes.” 

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