LAUSR

Optimal dosing of vancomycin in neonates remains a matter of debate despite the frequent use of vancomycin in neonatal intensive care units (NICUs). The optimal use of vancomycin requires knowledge of its pharmacokinetics (PK) and pharmacodynamics (PD) properties in neonates. The ratio of 24‐hour area under the concentration versus time curve to minimal inhibitory concentration (AUC24/MIC) was shown to be the best PK/PD surrogate marker of vancomycin efficacy. The target of AUC24/MIC ≥ 400 (where AUC24 and MIC are expressed as mg h/L and mg/L, respectively) is most commonly used in neonatal vancomycin PK/PD studies. However, it was originally defined in adult methicillin‐resistant Staphylococcus aureus (MRSA) pneumonia and was never validated in neonatal Staphylococci septicaemia. Moreover, this AUC24/MIC target level of 400 is based on total vancomycin concentration, while Smits et al recently demonstrated that the fraction unbound (FU) of vancomycin is much higher in neonates (median 0.9) compared with that in adults (median 0.6). Using PK/PD simulation, we have explored the impact of this recent finding on vancomycin dosing in neonates. It is important to first introduce two different concepts for vancomycin dosing optimization in neonates.