Geriatric psychopharmacology: Pharmacokinetic and pharmacodynamic considerations

Older adults represent the fastest growing demographic in both developing and developed countries. Understanding pharmacokinetic and pharmacodynamic principles relevant to psychopharmacology in geriatric patients is increasingly important to optimize psychiatric treatment. This review discusses the four pharmacokinetic processes (absorption, distribution, metabolism, and excretion) with regard to age-related changes. These include a generally slower rate of absorption, increases in the ratio of adipose to lean body mass and volume of distribution of medications, reductions in phase I metabolism, and decreases in renal function. In addition, this review discusses pharmacodynamic factors relevant to pharmacotherapy in older age, such as changes in receptor density and homeostatic and regulatory mechanisms. Geriatric psychopharmacology will benefit from an expanding evidence base as research on pharmacokinetics and pharmacodynamics increasingly includes older individuals.