High-dose continuous infusion of piperacillin/tazobactam via elastomeric pump in a pediatric patient with Kartagener syndrome: pharmacokinetic target attainment and clinical outcome.

Multidrug-resistant Achromobacter xylosoxidans infections in pediatric patients with primary ciliary dyskinesia (PCD) often require prolonged intravenous therapy. We evaluated the pharmacokinetics of continuous infusion piperacillin/tazobactam (16 g/2 g daily) in a 13-year-old male with situs inversus and chronic otitis media transitioned from hospital-based electronic infusion to home-based Outpatient Parenteral Antimicrobial Therapy (OPAT) using elastomeric pumps. Plasma concentrations were measured by Therapeutic Drug Monitoring (TDM), and tissue exposure was estimated using conservative penetration coefficients. Drug concentrations consistently remained above the MIC (≤2 mg/L). During hospitalization, steady-state concentrations were stable (27.2-29.0 mg/L; CV 4.5%), whereas during OPAT they were higher and more variable (53.9-80.1 mg/L; CV 20.1%), consistent with the known non-linear delivery profiles of elastomeric devices. Despite this variability, TDM confirmed sustained supratherapeutic exposure, with estimated tissue concentrations remaining >5-fold above the MIC. Clinical resolution was achieved without adverse events, supporting the role of TDM-guided OPAT in difficult-to-treat infections.