Which pharmacokinetic changes in older adults necessitate careful dosing and monitoring?

• A. No pharmacokinetic changes with aging
• B. Changes in absorption, distribution, metabolism, and excretion
• C. Uniform pharmacokinetics across all ages
• D. Improved drug clearance in older adults

Answer: (B)

Aging brings predictable changes in pharmacokinetics that require careful dosing and monitoring to maintain effectiveness while avoiding toxicity. All four processes—absorption, distribution, metabolism, and excretion—can be altered in older adults. Absorption may be slower or altered due to changes in gastric emptying and pH; distribution shifts because body composition changes (more fat, less total body water and lean mass) affect how drugs spread and reach target tissues; metabolism can slow with reduced hepatic blood flow and liver mass, lengthening the time a drug stays active; excretion commonly declines with reduced kidney function, raising the potential for drug buildup. Because of these intertwined changes, dosing often needs adjustment and closer monitoring is essential.

Other statements imply there are no pharmacokinetic changes with aging, that PK is uniform across ages, or that drug clearance improves with age, which contradicts how aging actually affects drug processing.