Obesity alters the movement through the body of several antibiotics, including vancomycin. Based on literature to date, total body weight should be used to determine dosages and shorter dosing intervals may be needed. However, hospitals have different approaches to managing vancomycin in this patient population. The most common example is not exceeding a dose of 2,000mg of vancomycin at one time in these patients. However, some institutions including the Charleston Area Medical Center do not have a set maximum one time dose. To date, a study has not been done comparing two different dosing regimens in obese patients to determine if having a maximum dose cap is beneficial.

This research study is attempting to add to the limited existing body of literature regarding vancomycin dosing in obese patients. The investigators hypothesize that optimizing the initial or loading vancomycin dose that obese patients receive will decrease the time to target concentrations. For this study, obese adult patients will be randomized to receive either 1) a loading dose of 20 mg/kg with a maximum dose up to 2,000mg OR 2) a loading dose of 20 mg/kg with a maximum dose of up to 4,000mg. The study's primary aim is to determine differences in the time needed to achieve target vancomycin concentrations and the occurrence of adverse events.

Inclusion Criteria:

• Patients ≥18 years of age who present to the Charleston Area Medical Center-Memorial Hospital Emergency Department
• Weight >100kg
• Infection requiring intravenous vancomycin and admission to Charleston Area Medical Center-Memorial Hospital

Exclusion Criteria:

• Any patient <18 years of age
• Patients on dialysis or with unstable renal function (a change of >0.5 mg/dL in SCr concentration in patients with a SCr of <2 mg/dL or a 20% change in SCr in patients with a SCr of ≥2 mg/dL)