OBJECTIVES: Adverse drug reactions (ADR) are an important cause of morbidity and mortality. We analysed trends in hospital admissions associated with ADRs in English hospitals between 1999 and 2008. DESIGN: Data from the Hospital Episode Statistics database were examined for all English hospital admissions (1999-2008) with a primary or secondary diagnosis of an ADR recorded. SETTING: All NHS (public) hospitals in England. MAIN OUTCOME MEASURES: The number of admissions and in-hospital mortality rate with a primary (codes including 'adverse drug reaction', 'drug-induced', 'due to drug', 'due to medicament' or 'drug allergy') or secondary diagnosis of ADR (ICD-10 Y40-59) were obtained and analysed. Further analysis for the year 2008-2009 was performed with regard to age, gender, proportion aged >65 yrs and total bed-days. RESULTS: Between 1999 and 2008, there were 557,978 ADR-associated admissions, representing 0.9% of total hospital admissions. Over this period the annual number of ADRs increased by 76.8% (from 42,453 to 75,076), and in-hospital mortality rate increased by 10% (from 4.3% to 4.7%). In 2008, there were 6,830,067 emergency admissions of which 75,076 (1.1%) were drug-related. Systemic agents were most commonly implicated (19.2%), followed by analgesics (13.3%) and cardiovascular drugs (12.9%).There has been a near two-fold increase in nephropathy and cardiovascular consequences secondary to drugs and a 6.8% fall in mental and behavioural disorders due to drugs. Conclusions ADRs have a major impact on public health. Our data suggest the number of ADR admissions has increased at a greater rate than the increase in total hospital admissions; some of this may be due to improved diagnostic coding. However, in-hospital mortality due to ADR admissions also increased during the period. Our findings should prompt policymakers to implement further measures to reduce ADR incidence and their associated in-hospital mortality, and methods to improve the recording of ADRs
