A descriptive case series of the relationship between maintenance of conservative PK/PD efficacy thresholds of dalbavancin over time and clinical outcome in long-term treatment of staphylococcal osteoarticular infections

Abstract

To describe the relationship between maintenance of pharmacokinetic/pharmacodynamic (PK/PD) dalbavancin efficacy thresholds over time and clinical outcome in a case series of patients who underwent therapeutic drug monitoring (TDM) during long-term treatment of staphylococcal osteoarticular infections (OIs). Patients who received two 1500-mg doses of dalbavancin 1 week apart for documented staphylococcal OIs, underwent TDM assessment, and had clinical outcome assessable at follow-up were included retrospectively. Dalbavancin concentrations ≥4.02 and/or ≥8.04 mg/L were identified as conservative PK/PD efficacy thresholds. The percentage of time of the overall treatment period with dalbavancin concentrations above these efficacy thresholds was calculated and correlated with clinical outcome. In total, 17 patients were included in this study. Long-term dalbavancin was used mainly for treating prosthetic joint infections (9/17, 52.9%). In 13/17 patients (76.5%), clinical outcome was assessable after at least 6 months of follow-up and was always successful (100.0%). In four of 17 patients (23.5%), clinical outcome is favourable after 3.7, 4.8, 5.1 and 5.3 months of follow-up, respectively. In most patients, both dalbavancin PK/PD efficacy thresholds were reached for most of the treatment period (%time ≥4.02 mg/L: 100% in 13 cases, 75-99.9% in two cases, 50-74.99% in two cases; %time ≥8.04 mg/L: 100% in eight cases, 75-99.9% in four cases, 50-74.99% in four cases, <50% in one case). These findings could support the idea that maintenance of conservative PK/PD efficacy thresholds of dalbavancin for the majority of the treatment period may represent a valuable approach in dealing efficaciously with long-term treatment of staphylococcal OIs.