Optimizing drug therapy is an essential part of caring for older people. Prescribing in this group has unique challenges because of high interindividual variability in pharmacological response and homeostatic mechanisms, and the fact that frailty, rather than age, predicts physiological responses to external stimuli. The effects of drugs and how they are handled by the body change with increasing age. With decreasing life expectancy, drugs used for secondary prevention might not be appropriate, particularly where their adverse effects impair quality of life.