Absorption to Excretion: The Aging Body’s Take on Drugs – A Review of Pharmacokinetic Changes and their Impact on Medication Management

Abstract Purpose of Review Aging alters pharmacokinetics in ways that significantly impact drug therapy, necessitating careful medication management in older adults. This review synthesizes established and emerging evidence on age-related changes in drug absorption, distribution, metabolism, and elimination, highlighting their clinical relevance. We aim to provide clinicians with practical strategies for optimizing pharmacotherapy in aging patients, including dose adjustments, drug selection, and therapeutic monitoring. Recent Findings Recent research has refined our understanding of how age-related physiological changes interact with polypharmacy, frailty, and comorbidities to influence drug handling. Studies reveal that renal clearance declines progressively with age, often requiring dose adjustments for renally excreted drugs. Hepatic metabolism is also affected, particularly for drugs with high hepatic extraction ratios, though the extent varies based on enzyme pathways. Additionally, emerging data suggest that transporter function, gut microbiome composition, and protein binding may further modify drug pharmacokinetics in older adults. These findings reinforce the importance of individualized medication management. Summary Age-related pharmacokinetic changes can alter drug exposure, increasing the risk of both toxicity and treatment failure. While renal decline is the most clinically significant factor, hepatic and transporter-mediated changes also contribute to variability in drug response. Clinicians must integrate pharmacokinetic principles with patient-specific factors to make informed prescribing decisions. By applying a nuanced approach to dose adjustments, drug selection, and monitoring, healthcare providers can enhance medication safety and efficacy in aging populations.