Why are older adults at higher risk for adverse drug reactions?

Older adults are at higher risk for adverse drug reactions primarily due to age-related changes in pharmacokinetics, which refer to how the body absorbs, distributes, metabolizes, and excretes drugs. As individuals age, several physiological changes occur, including alterations in body composition, organ function, and blood flow, all of which can significantly impact drug behavior in the body.

For instance, there is often a decrease in liver size and hepatic blood flow, which can reduce the metabolism of medications, leading to higher drug concentrations in the bloodstream and an increased risk of toxicity. Additionally, renal function tends to decline with age, affecting the elimination of drugs that are primarily excreted through the kidneys. This change can contribute to the accumulation of drugs and their metabolites, further increasing the likelihood of adverse reactions.

Furthermore, older adults may have an increased proportion of body fat and a decreased amount of lean muscle mass, which can alter the distribution of lipophilic and hydrophilic medications. These factors, combined with the common scenario of polypharmacy—where older adults often take multiple medications to manage various chronic conditions—add to the complexity of drug management, making this population particularly vulnerable to adverse drug reactions.

In contrast, increased muscle mass, higher metabolism rates