Population models misjudged vancomycin exposure more often with hepatic dysfunction

Design

Multicentre retrospective observational study

Population

157 adults on vancomycin with trough monitoring, 63 with hepatic dysfunction and albumin <2 g/dL

Primary outcome

≥30% deviation between Bayesian and population-predicted vancomycin AUC

Effect

Hepatic dysfunction aOR 2.26 (95% CI 1.10–4.62); higher AUC and trough ratios

This multicentre retrospective study included 157 adults on vancomycin with measured trough levels, 63 of whom had hepatic dysfunction with albumin below 2 g/dL. The authors compared each patient's AUC predicted from population pharmacokinetic parameters with the Bayesian AUC estimated from their actual trough levels.

Hepatic dysfunction more than doubled the odds that the two differed by 30% or more (aOR 2.26, 95% CI 1.10–4.62). Patients with hepatic dysfunction had higher exposures and trough ratios than predicted. The likely explanation is that low creatinine production in liver disease makes renal function look better than it is, so dose calculations overestimate clearance.

AUC-guided vancomycin dosing is increasingly standard, and many units start with a population-based dose and check levels later. This study suggests that in patients with liver disease and low albumin, waiting is riskier: exposure may already be well above target. It is a small, retrospective study, and it measured pharmacokinetic deviation rather than kidney injury, but the mechanism is well established.

• Consider measuring vancomycin levels early, after the first or second dose, in patients with hepatic dysfunction.
• Do not rely on a creatinine-based clearance estimate for the initial vancomycin dose in cirrhosis or low albumin.
• Use Bayesian dosing software where available rather than population estimates alone.
• Monitor renal function closely; higher than predicted exposure increases nephrotoxicity risk.
• Consider an alternative agent where levels cannot be measured promptly and the infection allows.

Why it matters

It shows that the standard starting calculation misjudges exposure most in the patients least able to tolerate it.

Don't overread it

The study measured how far estimates diverged, not whether early monitoring reduced kidney injury.

The statistics, in plain English

An adjusted odds ratio of 2.26 (95% CI 1.10–4.62) means hepatic dysfunction roughly doubled the odds of a large mismatch between predicted and actual exposure, after accounting for creatinine clearance. The wide interval reflects only 157 patients.

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