Background and Importance Antithrombotic Drugs (AD) belong to a therapeutic group considered as high-risk medication and they are a high priority in patient safety strategies.

Aim and Objectives To analyse pharmaceutical interventions according to ADs at the Emergency Department (ED), and to evaluate the factors that could influence the acceptance of pharmaceutical recommendations.

Material and Methods Prospective, longitudinal, observational study was conducted over a 9-month period. We selected pharmaceutical interventions performed by emergency medicine pharmacists in patients receiving ADs during the ED journey. A complete pharmacotherapeutic review was performed for each patient in order to detect drug-related problems (DRP) and a recommendation was issued to the responsible physician.

Collected data sex, age, number of chronic medications, polymedication (simple polymedication 5–9 drugs; extreme polymedication >9 drugs), patient clinical complexity level (low, moderate, high), drug involved.

We analysed type of interventions and DRPs severity according to the National Coordinating Council for Medication Error Reporting and Prevention (NCC-MERP) that classifies the error according to the severity of the outcome (Category A: no error, Category B-D: error without harm, E-H: error with harm, I: death). Severity was not evaluated in patients whose clinical situation changed before considering intervention.

A Chi-squared test was applied for categorical variables. For quantitative variables, t-Student-test or the equivalent non-parametric Mann-Whitney U-test was used. Statistical analysis was performed using SPSS®V22.

Results In total, 809 patients with antithrombotic medications (AD) were assessed. A total of 237 interventions were performed in 227 patients (28.05): 59.9% men, 79±12.4 years, 59% had a medium-high complexity level and 60.8% had extreme polymedication.

Regarding the interventions performed, 75.9% related to indication (57.7% start new medication and 13.3% discontinuing medication) and 20.2% to posology. According to the DRP severity assessment, 206 interventions were classified following NCC-MERP:117C, 48B, 27A, 7D, 5F, 1G and 1I.

Concerning pharmaceutical interventions,72.6% were accepted,14.35% were rejected and 13.1% were related to patients whose clinical situation had changed, and the intervention performed was no longer considered appropriate. Regarding influencing factors, there was a non-significance trend for type C error severity to be accepted more frequently (OR2.03 CI 95% 0.91- 4.52) p=0.07.

Conclusion and Relevance Acceptance rate of pharmaceutical interventions was high. Most of the interventions were related to drug indication. More than a half of the DRPs were errors that reached the patient without causing harm. No factors had an influence on acceptance ratio

Conflict of Interest No conflict of interest.