Dalbavancin is a long-acting lipoglycopeptide that is highly effective against most Gram-positive bacteria [1,2]. This antibiotic is licensed for the treatment of acute bacterial skin and skin structure infections (aBSSSIs), as a single 1500 mg dose, or as separate single doses of 1000 mg and 500 mg one week apart, in patients with preserved renal function. Importantly, dalbavancin has a favourable pharmacokinetic and safety profile compared with other anti-Gram-positive antimicrobials. In particular, the long elimination half-life of approximately 14 days for dalbavancin indicates potentially adequate exposure lasting for several weeks. Consequently, dalbavancin use has recently been progressively extended to several off-label indications requiring long-term treatment, such as bone and joint infections, infective endocarditis and endovascular prosthetic infections [3]. Two population pharmacokinetic studies, one in patients undergoing orthopaedic prosthetic surgery [4,5], and the other in patients with osteoarticular infections [4,5], showed that a regimen of two 1500 mg doses one week apart may provide optimal target attainment against staphylococci, defined as a free area under the cure for 24 h/minimum inhibitory concentration (AUC24h/MIC) ratio >111.1, for up to 5–6 weeks.

Therapeutic drug monitoring (TDM) is a potentially valuable tool for optimising long-term treatment with antimicrobials. Targeting dalbavancin total plasma concentration at ≥4.02 mg/L or ≥8.04 mg/L may enable attaining this target against staphylococci with an MIC value up to the MIC90 (0.0625 mg/L) or to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) susceptibility breakpoint (0.125 mg/L), respectively [6].

Bayesian modelling is a potentially effective method for forecasting the duration that dalbavancin concentrations persist above these predefined thresholds, particularly considering that renal function may affect drug exposure. This might enable clinicians to predict the duration of optimal treatment in the context of long-term use, and to assess at which time point dalbavancin should be re-dosed.

The aim of this study was to assess the accuracy and precision of a new Bayesian method for forecasting the duration of optimal target attainment, defined as maintaining target plasma concentrations ≥4.02 mg/L or ≥8.04 mg/L, during long-term use for treating subacute and chronic infections.