Working definition of medication errors
| Type of errors | Working 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 transcription | Wrong 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 |
| Others | Drug not authorised, wrong site, wrong patients, etc |
| Medication error per 100 prescriptions | Number 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 percentage | Calculated median of weekly values of medication error percentages expressed at each phase |
| Errors per prescription | Number of errors found in a single prescription |
| Mean errors/patient | Mean 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.