Background: The emergency department (ED) is a crowded area with complex workflow. Broad spectrum antibiotics given within the first hour of recognizing sepsis have proven to lower the mortality rate. Initiating optimal dose of Vancomycin to attain targeted serum level is an important role of emergency physicians and pharmacists. Objective: To evaluate the efficacy and safety of Vancomycin loading dose (VLD) (25-35 mg/kg) in reaching the targeted Vancomycin serum trough level compared to regular dose (15-20 mg/kg) in ED. Study design and settings: A multicenter, retrospective, cohort study. Methods: The study was carried out in four hospitals in Saudi Arabia; patients who received VLD were matched in a 1:1 fashion based on age category and diagnosis suspected in the ED. Inclusion criteria were age ≥14 years, diagnosed with serious infections caused by methicillin-resistant Staphylococcus aureus (MRSA), and microbiology culture confirmed MRSA. Exclusion criteria were missing weight, SCr, or Vancomycin trough level, patient on dialysis therapy/continuous renal replacement therapies, and concomitant use of nephrotoxic drugs at ED. Results: Over the 1-year study period, a total of 3,746 patients were prescribed Vancomycin in the ED. 232 patients received VLD matched to 232 patients received regular dose. Mean dose were 25.3 mg/kg (±4.3) and 13.7 mg/ kg (±2.6) for VLD and regular dose groups, respectively. The targeted Vancomycin trough level was significantly reached with the VLD group within 24 hours post-initial dose vs regular dose [18.7 (±3.2) vs. 11.6 (±4.3), respectively, p < 0.0001]. No difference in SCr value was noted post-Vancomycin initial dose between VLD and regular dose groups [1.5 (± 1.5) vs. 1.4 (± 1.8), respectively, p = 0.735]. Nephrotoxicity incident was higher with VDL (33, 14.2%) compared to regular dose, but the difference was not significant (22, 9.5%, p = 0.117). Conclusion: VLD has a rapid effect in reaching the targeted Vancomycin serum trough level compared to regular dose with a low rate of nephrotoxicity effect. The finding supports the use of VLD in patients admitted to ED who were suspected to have serious infections caused by MRSA.

Keywords: Vancomycin, loading dose, emergency department, nephrotoxicity MRSA.