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Reports of morbidity, hospitalizations, and death associated with adverse drug reactions (ADRs) are increasing. Better identification of risk factors might alert physicians and pharmacists to patients with heightened ADR risk.
In a study in hospitalized patients aged 65 and older, cardiovascular and arrhythmic ADRs were the most common (25.3% of all ADRs), followed by gastrointestinal (18.0%), neurologic and neuropsychiatric (17.8%), electrolytic (13.1%), and dermatologic/allergic (11.7%) complications. Roughly 64% of ADRs were severe. Taking a higher number of drugs and having a history of ADR were the strongest predictors of ADRs, followed by heart failure, liver disease, having four or more medical conditions, and renal failure. Using five or more medications approximately doubled the risk, and patients taking eight or more medications could pretty much count on such an event (odds ratio, 4.07; events occurred in 87.5%).
Editorialists detailed the need for research on preventing ADRs by tapering or eliminating medications, but enumerated likely obstacles: Pharmaceutical companies and organizations are unlikely to fund such clinical studies; institutional review boards might not approve protocols that remove medications; and patients and families may be reluctant to participate because they are used to the concept that more drugs are better. The editorialists also point out that use of over-the-counter agents like gingko biloba, ginseng, red clover, aspirin, vitamin E, and nonsteroidal anti-inflammatory drugs is common and can also cause ADRs and drug interactions.
Onder G et al. Development and validation of a score to assess risk of adverse drug reactions among in-hospital patients 65 years or older: The GerontoNet ADR risk score. Arch Intern Med 2010 Jul 12; 170:1142.
Schneider EL and Campese VM. Adverse drug responses: An increasing threat to the well-being of older patients. Arch Intern Med 2010 Jul 12; 170:1148.
Comment
These findings are intuitive — adding more drugs increases risk for reactions, interactions, and difficulty in correct administration. When I see a drug list that includes dozens of medications, I always wonder whether the patient can manage to take the medications as prescribed, including at the prescribed frequency. Studies in dermatology suggest that even within a clinical study, patients do not use medications as prescribed. Unsurprisingly, ADR risk went up in patients with more comorbid medical conditions; these patients are likely to be prescribed more drugs. A reasonable conclusion would be to use caution in prescribing multiple drugs to older patients; reductions can often be accomplished by assessing whether the benefits of each medication outweigh the risks for an ADR. We must also consider the patient's ability to take medications as prescribed.