Understanding Pharmacokinetic Changes is Imperative

Rhonda Witte, BSc

It is one thing to know how the body changes with age, but it is another to understand the effects of these changes on the body. Decreased kidney size? A smaller liver? They may sound like minor changes, but it is crucial to understand the significance of such age-related changes in terms of selecting appropriate drug therapy. Geriatric clinical pharmacology is not a large part of the general practice of medicine but with an increasing elderly population, greater knowledge in this area is required.1 What must be kept in mind is that it is not just about what drugs should be prescribed to the elderly--it is about the right drugs that should be prescribed to a geriatric patient on an individual basis.


Fundamental to geriatric medicine is the understanding of age-related changes in pharmacokinetics. Such changes have profound impacts upon drug usage in the elderly population. When ignored, severe complications and even death can result from pharmacotherapy. What makes the situation even more complicated is that pharmacokinetic changes vary with the individual. Therefore, each patient must be treated with a highly individualized approach2 and one patient's situation cannot set the standard for other patients to follow.

Pharmacokinetics refers to time-dependent changes of drug concentration and their metabolites in the body, or more simply, what the body does to a drug.