Drug dosage in the elderly. Is it rational?

Area of Science:

• Geriatric Pharmacology
• Clinical Pharmacology
• Drug Metabolism and Disposition

Background:

• Aging leads to reduced organ function, altered body composition (less water, more fat), and decreased receptor sensitivity.
• Key pharmacokinetic changes in the elderly include diminished kidney excretory capacity and altered drug distribution and bioavailability.
• Pharmacodynamic changes, such as reduced cardiovascular sensitivity and increased central nervous system vulnerability, also impact drug efficacy and safety.

Purpose of the Study:

• To review age-dependent changes in body function and composition relevant to pharmacotherapy in the elderly.
• To discuss pharmacokinetic and pharmacodynamic alterations affecting drug disposition and response in older individuals.
• To highlight the importance of individualized drug dosage adjustments and therapeutic drug monitoring in geriatric patients.

Main Methods:

• Review of age-related physiological changes impacting drug pharmacokinetics (absorption, distribution, metabolism, excretion).
• Analysis of pharmacodynamic shifts, including altered receptor sensitivity and organ system responses.
• Discussion of methods for dose adjustment, including population-based equations and patient-specific clearance calculations.
• Emphasis on the role of therapeutic drug monitoring and plasma drug concentration measurement.

Main Results:

• The elderly exhibit decreased kidney excretory capacity, necessitating consideration as renally insufficient patients.
• Drug metabolism decline is less pronounced than excretion changes, but volume of distribution and oral bioavailability can be altered.
• Pharmacodynamic changes, particularly in the cardiovascular and central nervous systems, increase vulnerability to adverse drug effects.
• Individualized dose adjustments based on drug clearance are superior to average adjustments due to significant inter-individual variability.

Conclusions:

• Pharmacotherapy in the elderly requires a thorough understanding of age-related physiological changes.
• Individualized dosing strategies and therapeutic drug monitoring are essential for optimizing drug therapy and minimizing risks in older adults.
• Further research into drug pharmacokinetic-pharmacodynamic relationships in the aged is critical for establishing optimal therapeutic targets.