Introduction and Objective: Medical errors and adverse events are among the major causes of avoidable deaths and costs incurred on health systems all over the world. Medical errors are among the main challenges threatening the safety of patients in all countries and one of the most common types of medical errors is medication errors. This study aimed to determine the frequency, type, and causes of medication errors in the emergency and pediatric wards of hospitals affiliated to Tehran University of Medical Sciences in 2017.

Materials and Methods: This study was a cross-sectional descriptive study which was conducted on 423 nurses working in teaching hospitals affiliated to Tehran University of Medical Sciences in 2017. The subjects were selected using the stratified sampling method. A total of 49 teaching hospitals in Tehran are affiliated to Tehran University of Medical Sciences and they are divided into two groups of general and specialized hospitals. Of all, 10 general hospitals and 14 specialized hospitals were randomly selected. The required data was collected using a three-part questionnaire. Using the SPSS software (version 18), the collected data was analyzed by means of ANOVA, Pearson Correlation Coefficient, and t-test and the results were reported as frequency, percentage, mean, and standard deviation.

Results: According to the results of this study, the mean total number of medication errors that occurred within one month in the pediatric and emergency wards was roughly 41.9 cases, as stated by the nurses. The mean number of medication errors was higher in men than in women. Also, the two variables of gender and the type of shift work were related to medication errors; specifically, it was higher first in the evening and night shifts and then in the morning and evening shifts, respectively. Also, the number was higher in night shifts than in the morning shifts. The most common types of medication errors were: administration of the drugs at the wrong time, using a wrong technique of administration, wrong dosage, forgetting the dosage of the drug, administrating additional doses, administrating the drug to a wrong patient, and following the oral orders of physicians. On the other hand, the most common causes of medication errors in clinical wards were the following: illegible physician orders, shortage of manpower and high workload, incomplete physician orders, the use of lookalike and sound-alike drugs, absence of pharmacist/pharmaceutical expert in the ward, lack of dosage forms appropriate for children, and lack of adequate training regarding drug therapy.

Discussion and Conclusion: Considering the results of this study, it is necessary to reduce the workload and working hours of nurses, increase medical staff’s awareness of the significance of medication errors, revise the existing techniques of drug prescription, and update the indices of human resource in hospitals. It is also necessary to correct the process of naming and selecting the dosage forms of drugs by the industry.