Which change affects drug distribution in older adults?

As people age, one of the significant physiological changes is the decrease in lean body mass. This decrease impacts drug distribution because many medications are distributed in body tissues, including muscle. Lean body mass serves as a reservoir for certain drugs, meaning that a reduction in muscle mass can lead to higher concentrations of these medications in the bloodstream. Consequently, older adults may experience increased sensitivity to medication effects or a higher likelihood of adverse drug reactions, necessitating careful monitoring and possibly dosage adjustments.

The other factors listed do not accurately represent the typical changes in older adults that would affect drug distribution. For instance, total body water generally decreases with age, which contradicts the first option. Additionally, improved metabolic rate is not a common change with aging; metabolic processes tend to slow down, affecting drug metabolism rather than distribution. Finally, higher cardiac output is not typically associated with older adults, as it often declines with age; this decrease can also influence how well drugs are absorbed and distributed throughout the body.