A nurse is reviewing a new medication order for a geriatric client. Which pharmacokinetic factor is most likely to be affected by the client's age?

A. Metabolism: While hepatic metabolism can decrease with age, the reduction is often variable and depends on liver function. Some medications are metabolized efficiently even in older adults, so metabolism is not always the most significantly affected pharmacokinetic factor. B. Absorption: Aging has minimal effect on gastrointestinal absorption. Most oral medications are absorbed similarly in geriatric clients as in younger adults, so absorption is generally not significantly altered. C. Distribution: Age-related changes in body composition, such as increased fat and decreased lean body mass, can alter drug distribution. However, these changes primarily affect lipophilic drugs and are less universally impactful than excretion. D. Excretion: Renal function declines with age due to decreased glomerular filtration rate and renal blood flow. This reduction significantly affects the elimination of many drugs, increasing the risk of drug accumulation and toxicity. Monitoring renal function is critical when dosing medications in geriatric clients.