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Magnitude of error: a review of wrong dose medication incidents reported to a UK hospital voluntary incident reporting system
  1. Gillian F Cavell,
  2. Deepal Mandaliya
  1. Pharmacy Department, King's College Hospital NHS Foundation Trust, London, UK
  1. Correspondence to Gillian F Cavell, Pharmacy Department, King's College Hospital, London SE5 9RS, UK; gillian.cavell{at}


Objectives Our aim was to review medication-related incidents reported to a hospital voluntary incident reporting system to identify and quantify the magnitude of wrong dose errors.

Methods The study was a retrospective review of medication-related incidents reported over a 7-year period at a large acute teaching hospital in the UK, providing secondary and tertiary care for a range of clinical specialties. Medication-related incident reports submitted from all clinical settings were reviewed. Incidents submitted under the categories ‘wrong dose’, ‘wrong dose preparation’, ‘wrong rate’ or ‘wrong quantity’ and describing situations where incorrect doses were prescribed, dispensed or administered were analysed. Magnitudes of medication overdoses and underdoses reported from adult and paediatric settings were calculated. Stage of the medicines process and drug classes most commonly involved in wrong dose errors were described.

Results Of 12 006 reported medication incidents, 1568 described ‘wrong-dose’ errors: 702 (44.8%) were prescribing errors, 223 (14.2%) were dispensing errors and 643 (41%) were administration errors. Overdoses were reported more frequently than underdoses. 926 (59%) of reported wrong dose errors were overdoses, 464 (29.6%) were underdoses; the magnitude could not be determined in 178 (11.4%) of reports. Twofold and 10-fold overdoses and underdoses were the most commonly reported error magnitude, although dosing errors across a wide range of magnitudes were reported. Incidents were reported from paediatric wards (491, 31.3%), non-paediatric wards and clinical settings (880, 56.1%) and pharmacy (197, 12.6%). Prescribing errors (702, 45.9%) were reported more commonly than administration (643, 41%) and dispensing errors (223, 14.2%). Drugs acting on the central nervous system, cardiovascular drugs and anti-infectives were the drug classes most commonly involved.

Conclusions Wrong dose errors occur across all inpatient settings. Wrong dose errors of all magnitudes are possible, but twofold and 10-fold errors occur most frequently. Drug classes involved in wrong dose incidents reported to a voluntary reporting system in a large acute hospital are similar to those identified using other methodologies. Harms and potential harms associated with specific drugs and error magnitudes need to be identified to inform quality improvement work to reduce the risk of patient harm.

  • clinical governance
  • risk management
  • drug overdose
  • inpatients
  • medication error
  • patient safety

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