Age is a major source of variation in drug response. Social, medical and physiological heterogeneity intertwines to complicate geriatric pharmacotherapy. Inappropriate and excessive use of medication may be the most significant treatable health problem in the elderly. Older people are especially sensitive to antipsychotics, which are disproportionately prescribed to them. Antipsychotic side effects and adverse reactions are intensified and protean in an older population, ranging from disabling to deadly. It is therefore essential that the use of antipsychotics be based on clear indications, guided by knowledge of both age-related and individual determinants of drug clearance and action. Prospective and frequent assessments for adverse effects are also essential.