Adverse drug events caused by medication errors in medical inpatients.
BACKGROUND
In view of growing concern in recent years regarding medication errors as causes of adverse drug events (ADEs), we explore the frequency and characteristics of error-associated ADEs in medical inpatients.


METHODS
All patients with ADEs or ADErelated hospital admission in a cohort of medical inpatients identified by "event monitoring" (SAS/CHDM database, Br J Clin Pharmacol 2000:49:158-67) were evaluated independently by two experienced physicians. ADEs were first divided into ADEs occurring during cohort stay (incident ADE) and ADE present prior to/at admission. ADEs were then grouped as error-associated ADEs (eADEs: indication error, missed contraindication, wrong dosage regimen or inadequate surveillance) and adverse drug reactions (ADRs: indication established, no contraindications, appropriate dosage regimen and adequate surveillance).


RESULTS
Among the 6383 patients analysed (100%), 481 (7.5%) experienced at least one incident ADE. Incident ADRs occurred in 457 (7.2%). Incident eADEs were recorded in 28 patients, corresponding to an eADE incidence of 0.4% (95% CI: 0.2, 0.7). Error types were missing/inappropriate indication (4 cases), missed contraindications (9), relative overdoses (8), absolute overdoses (3) and inadequate clinical surveillance (4). The responsible drugs included antithrombotics (6), cardiovascular drugs (5), antibiotics (5), hypnotics (4) and non-steroidal anti-inflammatory drugs (3). ADE-related hospital admissions were observed in 262 patients (4.1%); 183 (2.9%) were classified as ADRs and 79 (1.2%) as eADEs.


CONCLUSIONS
Incident eADEs were observed in 1 out of 250 patients and accounted for approximately 6% of ADEs. In contrast, eADEs accounted for 30% of ADE-related hospital admissions. Hence, in medical inpatients, eADEs represented a small fraction of total incident ADEs, whereas they contributed significantly to hospital admissions.
Hardmeier
Beat
B
Division of Clinical Pharmacology and Toxicology, Department of Medicine, University Hospital, Zürich, Switzerland.
Braunschweig
Suzanne
S
Cavallaro
Marzia
M
Roos
Malgorzata
M
Pauli-Magnus
Christiane
C
Giger
Max
M
Meier
Peter J
PJ
Fattinger
Karin
K
D016907:Adverse Drug Reaction Reporting Systems / Q000706:statistics & numerical data; D000368:Aged; D004363:Drug Utilization / Q000592:standards; D005260:Female; D006801:Humans; D007297:Inpatients / Q000706:statistics & numerical data; D008297:Male; D008508:Medication Errors / Q000145:classification* / Q000706:statistics & numerical data; D008510:Medication Systems, Hospital / Q000592:standards* / Q000706:statistics & numerical data; D008875:Middle Aged; D010343:Patient Admission / Q000706:statistics & numerical data; D013557:Switzerland