Adverse drug reactions as a cause of admission to an acute medical assessment unit: a pilot study

Background: In this pilot study, we have investigated the frequency of adverse drug reaction (ADR)-related admissions to an acute medical assessment unit. Although ADRs are thought to be responsible for 5% of hospital admissions, there have been no recent studies in the U.K. Objective: To pilot such a study for estimating the incidence of ADR-related admissions to an acute medical assessment unit. Method: Data were collected for 200 patients including details of concurrent illness, drug usage and reasons for admission. ADRs were assessed for causality using two previously published classification systems. Results: ADRs were responsible for admission in 15 (7.5%) patients, were present in an additional three (1.5%) patients and may have contributed to the deaths of two (1%) patients. Of the 15 ADRs suspected of causing an admission, three were considered to be 'possible' or 'unlikely', with the remaining 12 considered to be 'probable' or 'certain'. The proportion of patients identified in this study with ADR-related admissions is either similar to or larger than that found in comparable studies carried out in other hospitals. Nearly all ADRs were Type A reactions in that they were predictable and therefore potentially preventable. Conclusion: This study suggests that the proportion of ADR-related admissions has not decreased in the last decade and, given the increasing numbers of acute medical admissions, the absolute numbers may have actually increased. Furthermore, the nature of drugs causing admissions has not changed substantially over the last 20 years. Strategies to reduce the burden of ADR-related admissions are urgently needed.