Does Everything Get Slower with Age? Pharmacokinetics in the Elderly

The pharmacokinetics (PK) of a drug determine its systemic exposure and thereby affect its safety and efficacy. The multitude of physiological changes occurring with aging could impact drug absorption, distribution, metabolism or excretion, the key processes how the body is dealing with drugs. Another important, PK-related topic is the risk for relevant drug-drug interactions considering the number of drugs taken concomitantly by elderly patients. At the same time there are examples for relevant differences in the magnitude of drug effects, i.e. the pharmacodynamics of a drug in an aged vs. young population. These could be caused by differences in the number of receptors in the target organ as well as the response to receptor occupation, or by progressive reduction in homeostatic mechanisms, and could affect the efficacy as well as the safety [1]. Such age-related changes in the pharmacodynamics of a drug shall, however, not be addressed in this article despite their proven clinical relevance.

When discussing age-related changes in the PK of drugs, and in particular their consequences for dosing recommendations in aged patients, one needs to keep in mind that aging is a gradual, complex and progressive process and that there are no established biological age markers. While there is societal consensus to define elderly as individuals aged 65 years or older [1], dividing elderly in three age groups, such as 65 – 75, 76 – 85, and > 85 might help in better describing the aging processes [2].

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