Table 1

Working definition of medication errors

Type of errorsWorking definitions
Wrong dose*Unexplained deviation of more than 10% of normal, over/under the ordered dose
Wrong time*More than 30 min for emergency medicine
Wrong rate*Drug delivered slower or faster than the prescribed. Rate of infusion not mentioned. 24-hour volume of fluid more than 10% of over/under the ordered rate; or hourly rate more than 50% over/under the ordered rate
Wrong preparation*Incorrect dilution with correct drug dosage, mixing of incompatible drugs
Wrong route*Route other than the prescribed for the use in neonates
Omission*Failure to administer or omission of prescribed dose/drug type
Wrong transcriptionWrong copy of prescription in medical records for purpose of administration. Discrepancy in drug name, drug formulation, route, dose, dosing regimen, drugs which were not ordered
OthersDrug not authorised, wrong site, wrong patients, etc
Medication error per 100 prescriptionsNumber of errors described as above, divided by the total number of prescriptions analysed expressed in terms of 100 prescriptions (percentage of medication errors)
Median medication error percentageCalculated median of weekly values of medication error percentages expressed at each phase
Errors per prescriptionNumber of errors found in a single prescription
Mean errors/patientMean of errors occurred per patient included in the study in each phase
  • *Adapted from: American Society of Hospital Pharmacists. ASHP guidelines on preventing medication errors in hospitals. Am J Hosp Pharm 1993;50:305-14.