Medicine
Adverse Drug Reactions in Older Adults: Polypharmacy and Deprescribing
Quick fact
About 15% of older adults experience an adverse drug reaction severe enough to require hospitalization, and many of these are preventable through deprescribing unnecessary medications.
Why this is interesting
We all expect medicines to help, but in older adults the very act of taking many pills can become the cause of new symptoms. Have you ever wondered why that happens and what we can do about it?
Read the full explanation
Understanding Adverse Drug Reactions in Older Adults: Polypharmacy and Deprescribing
When someone takes multiple medications, the risks are not simply additive—they multiply. In older adults, the situation is even more delicate because the body processes drugs differently: the liver and kidneys may clear drugs more slowly, and the body is more sensitive to the effects of many drugs. Polypharmacy, commonly defined as taking five or more medications, increases the chance of adverse drug reactions (ADRs) dramatically. Think of it as a car with many optional add-ons: each one may be fine alone, but together they can overload the electrical system. Deprescribing is the thoughtful process of reducing or stopping medications that are no longer needed, are potentially harmful, or have a high pill burden. The goal is to maintain well-being while minimizing harm.
A deeper explanation
The mechanism behind ADRs in older adults with polypharmacy is multifactorial. First, pharmacokinetics change with age: reduced renal function and hepatic metabolism lead to higher drug concentrations that persist longer, raising the risk of toxicity. Second, pharmacodynamics shift: older adults often have increased sensitivity to medications such as benzodiazepines, causing sedation and falls, or to anticoagulants, increasing bleeding risk. Third, polypharmacy increases the chance of drug-drug interactions, where one drug affects the metabolism or clearance of another, amplifying or blunting effects. For example, a drug that inhibits the enzyme CYP3A4 can double the level of a second drug metabolized by that enzyme, turning a standard dose into a toxic one. Because many conditions co-exist in older adults, each with its own drug, the potential for harm is high. Deprescribing is not just stopping a drug—it is a systematic, multidisciplinary process that involves identifying potentially inappropriate medications, tapering doses to avoid withdrawal effects, and monitoring outcomes. The evidence shows that deprescribing can reduce falls, hospitalizations, and mortality. Understanding this mechanism empowers clinicians to balance the benefits and risks of each prescription, treating the patient, not just the list of diagnoses.