Elderly are characterized by impairment in the physiological functions, comorbidity and polypharmacy. These characteristics influence their pharmacotherapy. Age-related physiological changes influence drug pharmacokinetics and pharmacodynamics. Important pharmacokinetic changes are observed in drug metabolism in the liver and elimination via kidney. Drugs with blood flow limited metabolism are most prone to decreased metabolism. Renal elimination is decreased and clinically important for drugs which are predominantly eliminated from the human body via kidney and have low therapeutic index. Age-related changes in pharmacodynamics may occur at the receptor, signal transduction or homeostatic mechanisms levels. The most important physiological changes which concern pharmacotherapy are observed in central neural, cardiovascular and respiratory system. Regardless of the present knowledge of physiological changes in the elderly, a better understanding of changes could improve the efficacy and safety aspects of pharmacotherapy in elderly.