Ciprofloxacin Dosage Optimization in Cystic Fibrosis Through Therapeutic Drug Monitoring.

Background: Ciprofloxacin (CIP) is effective against many Gram-negative pathogens and penetrates well into respiratory secretions and pulmonary tissues, thus making it useful for treating respiratory infections in patients with cystic fibrosis (CF).

Methods: A 13-year-old patient with severe CF and an acute respiratory exacerbation from multidrug-resistant Pseudomonas aeruginosa was treated with 700 mg of CIP every 8 hours. Bronchial secretions confirmed that P. aeruginosa was sensitive to high doses of CIP. Pharmacokinetic monitoring using 2 blood samples estimated the AUC24 at 50 hours*mg/L. This led to an increase in CIP dosage to 850 mg three time a day (TID), then to 1000 mg TID, and finally to 1200 mg every 6 hours.

Results: CIP pharmacokinetics can vary significantly, particularly in patients with CF due to increased clearance, ultimately resulting in shorter half-lives and higher risks of therapeutic failure and resistance. Therapeutic drug monitoring helps when adjusting dosages to maintain effective blood concentrations.

Conclusions: This case underscores the role of therapeutic drug monitoring in optimizing CIP dosing for patients with CF and highlights the necessity for close collaboration between clinicians and pharmacologists to ensure effective antibiotic exposure.