Adverse drug events in hospitals: a systematic review.

The objective of this study was to evaluate studies on the occurrence of adverse drug events (ADEs) in hospitals in order to learn about their frequency and characteristics, comparing the methods for identifying them and the various definitions. A search was conducted on MEDLINE and identified studies published from 2000 to 2009. Inclusion criteria were: studies in populations not selected for specific diseases or drugs and ADEs that occurred during hospitalization. Twenty-nine studies were selected, displaying multiple sources of heterogeneity, including differences in the study populations, surveillance techniques, definitions of ADEs, and indicators. The proportion of patients with ADEs ranged from 1.6% to 41.4% of inpatients and the rates ranged from 1.7 to 51.8 events/100 admissions. A considerable share of these events could have been avoided. The findings show that ADEs in inpatients are a public health problem. However, further studies are needed to monitor these adverse events in order to effectively promote safe drug use.