Ciprofloxacin in critically ill subjects: considering hepatic function, age and sex to choose the optimal dose.

BACKGROUND: Pathophysiological changes often result in altered pharmacokinetics of ciprofloxacin in critically ill patients. Although ciprofloxacin clearance (CLCIP) substantially depends on kidney function in healthy volunteers, its relationship to measured creatinine clearance (CLCRM) is weak in critically ill patients.

OBJECTIVES: To assess the need for dose reductions in isolated or combined kidney and liver dysfunction in critically ill patients and to re-evaluate relationships between kidney parameters, demographics and ciprofloxacin pharmacokinetics.

METHODS: A population pharmacokinetic model was developed based on 444 ciprofloxacin serum concentrations from 15 critically ill patients with severe infections. CLCIP relationships to parameters reflecting hepatic function, CLCRM, Cockcroft-Gault creatinine clearance (CLCRCG), serum creatinine, sex, weight and age were explored. A simulation study was conducted to integrate knowledge from the new and previously published models.

RESULTS: Total bilirubin was identified as a hepatic parameter with a clear relationship to CLCIP. A significant relationship between CLCIP and CLCRCG could be attributed to age and sex only. CLCIP was not associated with CLCRM. The predicted risk of potential overexposure (AUC > 250 mg·h/L) was low even with 1200 mg/day ciprofloxacin daily for patients with reduced CLCRCG (<30 mL/min: risk of 0.7%), while the risk was remarkably higher in elderly female patients with elevated bilirubin (risk of about 20% for 65-year-old women with total bilirubin of 4 mg/dL).

CONCLUSIONS: Bilirubin, age and sex should be considered to assess the need for dose reductions. For MICs ≤0.25 mg/L, it might be appropriate to reduce the dose to 400 mg/day for elderly female subjects with high bilirubin.