Spontaneous reporting of adverse drug reactions : Possibilities and limitations

Abstract: Adverse drug reactions (ADRs) constitute a major problem in society and in drug therapy. They are a common cause of short-term hospitalization, prolonged hospitalization and death. Spontaneous reporting of ADRs remains one the most effective methods for detecting new and serious drug reactions. In Sweden physicians are legally required to report fatal and serious ADRs. We know from previous studies that there is a substantial degree of under-reporting of ADRs also in Sweden.Attitudes towards reporting of ADRs among physicians in the northern region of Sweden were investigated using a questionnaire. The most important factor for not reporting ADRs among physicians and general practioners in our region was that the reaction was considered to be well known. However, their attitudes could also allow for a considerable rate of under-reporting.The effect on the reporting rate when nurses received instruction and were encouraged to report ADRs was studied. During a 12-month study period, 18 ADR reports with a total number of 22 ADRs were sent in by the nurses participating in the study to test nurses as reporters of ADRs.Using the Swedish ADR database, we calculated the risk of agranulocytosis associated with the use of metamizole by using consumption data from the case records of scrutinized patients’ and stored prescriptions. Over the period from 1996 to 1999, ten cases of agranulocytosis during treatment with metamizole were reported to SADRAC. Metamizole was prescribed to 666 (19%) inpatients during the 3-month study period and 112 prescriptions were identified at the participating pharmacies. Thirty-eight percent of them indicated treatment for more than 15 days. Making certain assumptions, the calculated risk of agranulocytosis was one out of every 31 000 inpatients and one out of every 1400 outpatients. The degree of under-reporting of serious ADRs was studied in five hospitals. More than 1300 case records were scrutinized and among these we found 107 cases that according to current rules for ADR reporting, should have been reported. Only fifteen of these were found in the SADRAC database, indicating a under-reporting rate of 86%.The effect on the reporting rate of ADRs was studied in an intervention study in which a small economical inducement was given to those who reported ADRs.The effect of a small economical stimulation to increase the reporting rate was studied. From the intervention area we received 62 suspected ADRs compared with 50 from the control area. The increase in the number of reports was 59% compared with an unchanged reporting rate from the control area.The physicians in northern Sweden have a relatively good knowledge of the existing rules for ADR reporting. Nurses could play an important role in detecting and reporting suspected ADRs.The risk of developing an metamizole induced agranulocytosis is considerably increased if metamizole is given to patients for a longer time than recommended. The rate of reported ADRs is very low, also for serious and fatal reactions. An increase in the reporting rate of suspected ADRs was observed during study period.