Question 1

Will this vancomycin calculator remain free of charge?

Accepted Answer

Yes, this website will continue to be available at no cost.

Question 2

Why did you pick Buelga 2005 as a general hospitalized Bayesian model?

Accepted Answer

The Buelga model is commonly used for Bayesian vancomycin dosing and has been studied across various patient populations. Although it was initially developed for patients with hematological malignancies, it has also been validated in a broader hospitalized population. Other models, such as Goti et al. (2018), may offer lower bias and greater precision, but they use a two-compartment approach. One of this calculator's main goals is to make vancomycin dose calculations transparent. Since clinicians and pharmacokinetic textbooks commonly use one-compartment pharmacokinetics, the calculator considers only one-compartment Bayesian models.

Question 3

What does it mean if the calculator indicates that Bayesian modeling did not demonstrate a good fit for the patient data?

Accepted Answer

This message appears when the available patient information cannot produce a model that adequately matches the measured vancomycin concentration. It may indicate a data-entry mistake or a laboratory error. For example, a patient with severely impaired renal function (CrCl 20 mL/min) who receives a very large dose (15 mg/kg IV every 8 hours) would be expected to have a high trough concentration. Even after adjusting vancomycin clearance (CLvanco) and volume of distribution (Vd), the model may be unable to match the measured drug level. When the model is validated, a high sum of squares (SS) indicates that the predicted values do not fit the patient data well.

Question 4

Why doesn't this calculator use a volume of distribution (Vd) of 0.7 L/kg? Some pharmacokinetic textbooks use this value?

Accepted Answer

A Vd of 0.7 L/kg is a convenient population-based estimate, but research shows that actual values can vary considerably. They may be below 0.5 L/kg in patients with morbid obesity or exceed 1 L/kg in non-obese critically ill patients. By default, the calculator uses Bayesian population estimates to select a suitable pharmacokinetic model based on factors such as critical illness and obesity. Users can also choose from alternative Vd options, including 0.7 L/kg using the Bauer method.

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