Pharmacologic Principles and Elderly Patients
Pharmacologic principles apply differently to elderly patients. Compared with younger patients, elderly patients have less lean body mass because of a decrease in muscle bulk, less body water and albumin, and an increased relative percentage of adipose tissue. These physiologic differences alter tissue binding and distribution of a drug. Human renal function declines with age; both hepatic perfusion and enzymatic activity are variably affected as well. Older patients tend to take more medications for chronic conditions than do younger patients, and many of the drugs they use are processed simultaneously by their already-compromised metabolic systems.
The pharmacokinetic processing of drugs in elderly patients is thus significantly altered, extending the effective half-life of most medications. The pharmacodynamic action of a drug is often independently potentiated in these patients. The increase in both drug effect and adverse effects occurs even when the dose is decreased in consideration of these pharmacokinetic differences. Thus, the pharmacotherapeutic effects and toxicity of a medication may be altered simply by the aging process, independent of drug dosage. Accordingly, the selection of a specific therapeutic agent should be guided by the general health and age of the individual, as well as by concomitant medication used by the patient.
Awwad S, Mohamed Ahmed AHA, Sharma G, et al. Principles of pharmacology in the eye. Br J Pharmacol. 2017;174(23):4205–4223.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.