OBJECTIVES. The aims of this study were (1) to collect data on the stability of antibiotics in portable pumps for the treatment of bronchial superinfection in patients with cystic fibrosis and (2) to provide guidelines for prescribers.

METHODS. The stability over 72 hours, in portable pumps stored at 35°C, of piperacillin plus tazobactam, ticarcillin plus clavulanic acid, cefsulodin, cefepime, and aztreonam was checked at 3 different concentrations. Stability was assessed through visual examination, pH measurements, and direct measurements of drug concentrations by using high-performance liquid chromatography. All parameters were measured at time 0, time 0 plus 24 hours, and time 0 plus 72 hours.

RESULTS. Degradation rates for penicillin plus β-lactamase inhibitor combinations remained <10% at time 0 plus 24 hours for all drugs, but the rate for piperacillin reached 12% for the highest concentration tested. The cephalosporins cefepime and cefsulodin had significant respective degradation rates of 18% and 28% at time 0 plus 24 hours and 60% and 68.5% at time 0 plus 72 hours, which were linked to the storage temperature. Aztreonam seemed to be stable over 72 hours.

CONCLUSIONS. This work provides data on drug stability that were lacking, allowing recommendations for physicians to optimize the safety and efficacy of antibiotic treatment of patients with cystic fibrosis. Piperacillin plus tazobactam and ticarcillin plus clavulanic acid infusions must be limited to 24 hours, and patients receiving cefepime or cefsulodin must wear a cold pack close to the ambulatory drug-delivery device during the infusion.

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