A previous ALiEM post from 2013 by an EM pharmacist colleague argued the case against one-time vancomycin doses in the ED prior to discharge. The take-home points from this post were:

    1. No evidence that a one-time vancomycin has any benefit
    2. This practice is not recommended by the Infectious Diseases Society of America (IDSA)
    3. May extend the patient’s ED stay by at least an hour for the IV infusion, depending on the dose
    4. Increases the cost of the ED visit (e.g., IV line, medication, RN time)
    5. Pharmacokinetically 1 dose of vancomycin doesn’t make sense
      • Vancomycin 1 gm IV x1 provides sub-therapeutic levels for patients with normal renal function
      • Efficacy is based on overall exposure (e.g., AUC/MIC) achieved with repeated dosing over several days
    6. Subtherapeutic vancomycin concentrations lead to development of resistance

Despite the above points, a one-time dose of vancomycin prior to the patient being discharged on an oral regimen is a common practice [1].


As stated above, a single dose of vancomycin is unlikely to provide a therapeutic benefit and may only serve to reassure clinicians. The 2020 consensus guidelines regarding vancomycin monitoring for serious MRSA infections reinforce the recommendation of achieving an AUC0-24/MIC ratio of ≥400, as a ratio <400 increases resistance and has inferior efficacy [2]. Since the AUC is dependent on overall time of exposure plus concentration, a single dose for an average patient with normal renal function is not adequate (Figure 1). The graph below also demonstrates how long it generally takes for vancomycin to reach steady state when patients receive a dose every 8 hours.


*The estimated AUC above assumes a 30 yo male that weights 70kg and is 6′ tall with a serum creatinine of 1.0 mg/dL.

A randomized trial conducted at Christiane Care Health System compared patients who received a vancomycin loading dose of 30 mg/kg or 15 mg/kg [3]. Just twelve hours after this initial dose, 34.6% of patients who received 30 mg/kg had vancomycin levels in the therapeutic range (trough >15 mg/L) vs. 3% of patients who received 15 mg/kg (p < 0.01).

Bottom Line

Even large vancomycin loading doses rarely achieve therapeutic levels after one dose. Therefore, if the plan is to discharge, skip the one-time dose altogether and choose an antimicrobial regimen that will be continued in the outpatient setting (e.g., doxycycline or sulfamethoxazole/trimethoprim if concerned for MRSA or cephalexin for most other patients).

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  1. Mueller K, McCammon C, Skrupky L, Fuller BM. Vancomycin use in patients discharged from the emergency department: a retrospective observational cohort study. J Emerg Med. 2015;49(1):50-57. doi: 10.1016/j.jemermed.2015.01.001. PMID: 25802166.
  2. Rybak MJ, Le J, Lodise TP, et al. Therapeutic monitoring of vancomycin for serious methicillin-resistant staphylococcus aureus infections: a revised consensus guideline and review by the american society of health-system pharmacists, the infectious diseases society of america, the pediatric infectious diseases society, and the society of infectious diseases pharmacists. Am J Health Syst Pharm. 2020;77(11):835-864. doi: 10.1093/ajhp/zxaa036. PMID: 32191793.
  3. Rosini JM, Laughner J, Levine BJ, Papas MA, Reinhardt JF, Jasani NB. A randomized trial of loading vancomycin in the emergency department. Ann Pharmacother. 2015;49(1):6-13. doi: 10.1177/1060028014556813. PMID: 25358330.
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP

Leadership Team, ALiEM
Creator and Lead Editor, Capsules and EM Pharm Pearls Series
Attending Pharmacist, EM and Toxicology, MGH
Associate Professor of EM, Division of Medical Toxicology, Harvard Medical School
Bryan D. Hayes, PharmD, DABAT, FAACT, FASHP


EM Pharmacist & Toxicologist @MassGeneralEM | Asst Prof @HarvardMed/@EMRES_MGHBWH | @ALiEMteam leadership | Capsules creator, ALiEMU | President, ABAT | #FOAMed
Mike O'Brien, PharmD

Mike O'Brien, PharmD

ALiEM Series Editor, EM Pharm Pearls
EM Clinical Pharmacy Specialist
Massachusetts General Hospital