Background Medication errors are a serious and complex problem in clinical practice, especially in intensive care units whose patients can suffer potentially very serious consequences because of the critical nature of their diseases and the pharmacotherapy programs implemented in these patients. The origins of these errors discussed in the literature are wide-ranging, although far-reaching variables are of particular special interest to those involved in training nurses. The main objective of this research was to study if the level of knowledge that critical-care nurses have about the use and administration of medications is related to the most common medication errors. Methods This was a mixed (multi-method) study with three phases that combined quantitative and qualitative techniques. In phase 1 patient medical records were reviewed; phase 2 consisted of an interview with a focus group; and an ad hoc questionnaire was carried out in phase 3. Results The global medication error index was 1.93%. The main risk areas were errors in the interval of administration of antibiotics (8.15% error rate); high-risk medication dilution, concentration, and infusion-rate errors (2.94% error rate); and errors in the administration of medications via nasogastric tubes (11.16% error rate). Conclusions Nurses have a low level of knowledge of the drugs they use the most and with which a greater number of medication errors are committed in the ICU. Electronic supplementary material The online version of this article (10.1186/s12913-019-4481-7) contains supplementary material, which is available to authorized users.

Aims The aim of this study was to identify the main medication errors, their causality and the highest risk areas in critical care. Design A descriptive, longitudinal and retrospective study. Methods We performed a systematic analysis of the prescription, transcription and administration records of 2,634 dose units of medications that were administered to a total of 87 critically ill patients during 2018. Results Final results have shown important medication errors and a high number of significant drug interactions; prescription phase had the highest mistake rate (71%) and cause of errors (68%); transcription stage had a more variable error typology. A significant correlation was observed between the presence of causes and contributing factors to error during the prescription and the commission of errors during the nurse transcription, being the main risk areas the time of antibiotic administration, dilution errors, concentration and speed of administration of high‐risk medications and the technique used for nasogastric tube drug administration. Conclusion In critical care, an intolerable number of medication errors are still committed, placing the origin of many of them in the causality and contributing factors identified in the prescription stage. Impact The origin of many of the medication errors and most interactions is in the prescription stage, being the nurse transcription (nurse intervention) in an important filter that prevents a considerable number of errors from finally reaching the patient. The schedule of administration of time‐dependent antibiotics, high‐risk medications and the technique of administering medications through a nasogastric tube are important risk areas for the commission of medication errors.