RESUMO
Elderly persons are particularly exposed to drug reactions, especially drug interactions subsequent to multiple prescriptions. It is also recognized that the drug risk is the leading hospital risk involving 1 to 10% of all hospitalized patients. An analysis of the avoidable nature of drug reactions leads to consideration of a sequence of 4 events leading to drug exposure: prescription, delivery, administration and compliance. Each event in this sequence corresponds to a distinct person: physician, pharmacist, nurse, patient. This suggests that the prevention of drug reactions in hospitalized elderly persons requires implementation of an "alert-causal attributability-avoidability-prevention" system by the healthcare teams where physicians, pharmacists, and nurses work in close coordination with the patient.