Background Previous studies have reported an error rate between 11.7% and 49.0% in the medication process for hospitalised children. Off-label use and diluting medicines increase the risk of error in paediatric patients, in addition to developmental differences among children. Health care organisations are developing strategies in an attempt to reduce those errors, caused by many factors involving many people.

Purpose To determine the overall incidence and incidence at different stages of medication errors (transcription, storage, preparation and administration stages) in a paediatric hemato-oncology ward.

Materials and methods We conducted a descriptive observational study of drug administrations in a paediatric hemato-oncology ward of a large teaching tertiary hospital in Spain. Data were collected on 21 days, including weekends, between February and March of 2013 and they were analysed by SPSS statistical software.

Medication errors were classified according with the updated classification of the Ruiz-Jarabo group (Otero et al., 2008). The error rate was calculated considering the number of doses with one or more errors as numerator and total opportunities of error (TOE) as denominator. TOE is defined as the total number of doses given, whether correct or incorrect, plus omitted doses.

Results 23 patients (52.2% female, 47.8% male, average age 6.0 [3.0–10.0] years old) were observed. Of 1116 doses administrated, 302 had at least one error, so error rate was 27.1% (95%, CI: 24,1%-30.3%) or 24.1% excluding wrong-time errors. Stages with higher error rates were preparation (43.8%) and storage (32.3%). Most common errors were related to photoprotection (66.7%), timing errors (15.8%) and incorrect preparation of suspensions (10.5%).

Pharmacological groups with higher error rates were cardiovascular (100.0%), gastrointestinal (61.9%) and nervous system (49.3%).

Conclusions The error rates we obtained were similar to those published before. Most common errors were related to failures in working protocols because medicines were never protected against light.

No conflict of interest.