Adverse drug events as a cause of hospital admission in the elderly

Background: Previous studies of adverse drug events (ADE) as a cause of hospital admission in the elderly have often been limited in their ability to assess fully the impact and potential for prevention because they either did not include all categories of ADE and/or did not assess severity and preventability. Aims: To assess the frequency, severity and preventability of ADE causing emergency medical admissions in the elderly. Methods: Cross-sectional survey of 219 patients aged 75 years and over who were consecutive unplanned admissions to acute medical units of the Royal Hobart Hospital in an 8-week period during August and September 1998. Results: Seventy-three of 240 (30.4%) admissions may have been a result of ADE. Patients admitted because of ADE were taking more drugs than those admitted for other reasons. Most ADE were adverse drug reactions to a single (46%) or multiple drugs (25%). Non-compliance, omission or cessation of indicated treatment accounted collectively for 26% of admissions. Of all ADE admissions 53.4% were considered definitely preventable. The commonest causative drugs were cardiovascular drugs (48.4%), and the commonest manifestations were falls and postural hypotension (24.1%), heart failure (16.9%) and delirium (14.5%). ADE categories in which a high proportion of admissions was both severe and definitely preventable were non-compliance and omission of indicated treatment. Conclusions: Adverse drug events are a common preventable cause of unplanned medical admissions in the elderly. Non-compliance and omission of indicated treatment are causes of ADE-related admissions that are both preventable and frequently associated with severe ADE.