Which process is affected by a decreased percentage of total body water in older adults during pharmacokinetics?

The correct answer is B, or distribution. In older adults, a decreased percentage of total body water affects pharmacokinetics significantly, particularly during the distribution phase.

As individuals age, there is a natural decline in total body water, which can lead to an increased concentration of water-soluble drugs in the bloodstream. This is because these medications have a smaller volume of distribution, meaning that there is less water available to dilute the drug. Consequently, this can intensify the effects and potential toxicity of these medications since they are not dispersed as thoroughly throughout the body.

The changes in body composition that occur with aging, including reduced total body water, lead to altered pharmacokinetic responses, making it crucial for healthcare providers to consider these factors when prescribing medications to older adults. Understanding how distribution is affected helps in anticipating drug levels and side effects, ultimately supporting safer and more effective medication management in this population.