Antibiotic stability in commercial peritoneal dialysis solutions: influence of formulation, storage and duration.

Peritoneal dialysis (PD)-associated peritonitis is treated by administration of antibiotics mixed with the PD solution. Data on antibiotic stability for solutions in current use are limited. The aim of this study was to determine the stability of cefepime, cephazolin and ampicillin in three commercial PD solutions. Antibiotics were added to the non-glucose compartment of the Gambro (Gambrosol®) and Fresenius (Balance®) multi-compartment systems and Baxter (Dianeal®) single-compartment (glucose 2.5%) PD solutions in a sterile suite. Antibiotic stability over 3 weeks was determined using both a bioassay of bacterial inhibition and antibiotic concentrations. The influence on stability and sterility of storage conditions was determined. The bioassay demonstrated the stability of all antibiotics for 9 days at room temperature and 3 weeks when refrigerated, except ampicillin in the Gambro solution, which displayed no bioactivity after 4 days. However, a ceiling effect in bacterial inhibition at higher antibiotic concentrations limited the ability of the bioassay to detect antibiotic degradation at relevant concentrations. Antibiotic concentrations varied with time but were comparable to the bioassay and supported stability in refrigerated solutions, except ampicillin in the Gambro solution. No bacterial contamination, marked colour change or precipitation occurred. This study supports the stability of cephazolin and cefepime in all three PD solutions and ampicillin in only the Baxter and Fresenius PD solutions. Antibiotic stability studies should ideally be conducted prior to registration and marketing of new PD solutions.