Prevalence, seriousness and effect of previous adverse drug reactions on prescribing during acute medical admission

Background Adverse drug reactions (ADRs) are associated with significant morbidity, mortality and cost. Knowledge of the prevalence of previous ADRs at admission highlights the potential burden of ADR risks to hospital in-patients. However, the proportion of acute medical admissions with previous ADRs and how this affects inpatient prescribing is uncertain. Objectives To determine the prevalence and seriousness of previous ADRs in newly admitted medical patients, and ascertain the effect of previous ADRs on choice of prescribed medications during acute hospitalisation. Also, we compared the seriousness of ADRs as classified by patients and standard definition. Setting Acute admissions within the medical directorate of a district general hospital serving a population of about 280,000 people in the north east of England. Method Newly admitted medical patients over a period of 8 weeks were prospectively screened to identify those with a previous history of ADR using patient interviews. Reviews of hospital notes and general practice summaries were undertaken for patients we were unable to interview. A structured form was used to collect relevant data from patients identified to have previous ADRs from the aforementioned sources. Main outcome measures Prevalence and seriousness of previous ADRs, and the proportion of acute medical prescriptions affected by previous ADRs. Results A total of 509 acute admissions were screened. Of these, 19.8 % had ADRs to previously prescribed medications. Whereas 62.7 % of patients deemed their ADRs to be serious, only 20.9 % of previous ADRs were so by standard definition. 18.8 % of previous ADRs affected choice of prescribed medications during the present admission but this was not influenced by the seriousness of previous ADRs. Conclusion The prevalence of previous ADRs at admission is high and significantly affects choice of drugs used during acute hospitalisation. There are clear inconsistencies between patient perspective and standard definition of the seriousness of ADRs which is likely to be due to patients' heightened subjective perception of harm.