Pharmacokinetics of intravenous ciprofloxacin for Legionella pneumonia during prolonged intermittent kidney replacement therapy: a case report and literature review

Abstract Background Legionella pneumophila is a gram-negative intracellular bacteria that causes pneumonia. In severe cases, combination antimicrobial therapy using azithromycin and ciprofloxacin is recommended and critical care management may be required. Ciprofloxacin requires dose adjustment during kidney replacement therapy; however, dosing guidance during prolonged intermittent kidney replacement therapy (PIKRT) is limited. A population pharmacokinetic (PK) study based on in vitro data suggested high doses would be required to meet pharmacokinetic/pharmacodynamic (PK/PD) targets. Case presentation We describe the PK of intravenous ciprofloxacin in a 71-year-old male with L. pneumophila pneumonia requiring PIKRT. Ciprofloxacin was administered at 400 mg IV every 12 h, in addition to azithromycin. Ciprofloxacin PK modelling described a terminal half-life of 10.7 h and an area under the curve over 24 h (AUC 0-24 ) of 130 mg·h/L. While PK/PD targets specific to L. pneumophila are not established, applying the reported median minimum inhibitory concentration (MIC) for Legionella (0.5 mg/L), and the gram-negative organism PK/PD target AUC 1–24 /MIC > 125, our data supports ciprofloxacin dosing of 400 mg IV every 12 h during PIKRT. Contrary to the prior PK study based on in vitro data, PIKRT did not contribute additional clearance of ciprofloxacin. Conclusions Ciprofloxacin 400 mg IV every 12 h achieved adequate exposure during PIKRT, supporting this dosing regimen for treating L. pneumophila pneumonia. Further studies are needed to establish definitive dosing guidelines in this setting.