Which scenario exemplifies age-related pharmacokinetic ADRs?

• A. In older patients, reduced absorption due to slowed GI motility.
• B. In older patients, unchanged drug metabolism.
• C. Reduced elimination in older patients, leading to increased concentration.
• D. In older patients, faster clearance.

Answer: (C)

The key idea is that age-related pharmacokinetic adverse drug reactions often come from reduced elimination, especially renal clearance, in older adults. As kidney function typically declines with age, drugs that are cleared by the kidneys aren’t eliminated as efficiently. This slows their overall clearance, prolongs their half-life, and raises plasma concentrations. Higher exposure increases the risk of dose-related toxicity and ADRs, particularly for drugs with a narrow therapeutic index.

Other scenarios don’t fit as well because absorption changes with aging are usually modest and aren’t the main driver of accumulation or toxicity, and metabolism is not universally unchanged in older adults (it can be reduced for some drugs). Faster clearance would actually lower drug exposure, which is not characteristic of aging.