[Factors that intervene in adverse drug reactions]

Drug prescriptions and adverse reactions occurring during 2 periods of 3 months in a department of medicine were analyzed by computer programs. Among 148 reactions suspected, 130 were considered definite or probable by one physician (1.6 reaction per 100 drug prescriptions). The patients who suffered from an adverse reaction were older, were hospitalized for a longer period of time and received more drugs than the others. The data were submitted to two physicians who were asked to determine the degree of probability of each reaction independently. There were many discrepancies between physicians' judgements (52% of the reactions) if one of them had a brief summary of the case history and the other had all the data available. The discrepancies were far fewer (18.1%) if both physicians had all the data available, and were due to the drug(s) suspected (8.8%) or to the influence of the disease (9.3%).