Stability of tobramycin and ceftazidime in icodextrin peritoneal dialysis solution

The data describing the compatibility of tobramycin and ceftazidime in icodextrin-based peritoneal dialysis (PD) solution is limited. The objective of this study was to assess the chemical stability of tobramycin and ceftazidime in icodextrin PD solution in polyvinyl chloride containers.

Commercially available 2-L bags of icodextrin 7.5% PD solution were used for each sample. Nine tobramycin study samples were prepared by adding 80 mg tobramycin HCl to each bag. Nine ceftazidime samples were prepared by adding 1000 mg ceftazidime to each bag. Three bags of tobramycin-icodextrin solution were stored under each of the following conditions: refrigeration (4 degrees C), room temperature (25 degrees C), and body temperature (37 degrees C). Three bags of ceftazidime-icodextrin solution were also stored at each of the respective temperatures. Samples were withdrawn from each bag immediately after preparation and at predetermined intervals (1, 2, 4, 6, 8, 12, 24, 48, 72, 96, 120, 168, and 336 hours after preparation). Solutions were visually inspected for precipitation, cloudiness, and discoloration at each sampling interval. All samples were immediately frozen (-80 degrees C) after collection and stored prior to assay. Total concentrations of tobramycin and ceftazidime in dialysate fluid were determined by high-performance liquid chromatography. The last time point when tobramycin or ceftazidime concentration was >90% from baseline was used to denote stability.

All solutions were clear in appearance and no color change or precipitation was observed during the study. For tobramycin, under refrigeration, a mean of 94.6%+/-2.3% of the initial concentration remained at 336 hours (14 days); at room temperature, 90.5%+/-4.3% remained at 168 hours (7 days); at body temperature, 90.0%+/-8.1% remained at 24 hours. For ceftazidime, under refrigeration, a mean of 98.0%+/-0.3% of the initial concentration remained at 168 hours (7 days); at room temperature, 91.6%+/-2.0% remained at 48 hours; at body temperature, 93.9%+/-1.1% remained at 8 hours. Stability was not assessed beyond these respective time points.

Premixed tobramycin-icodextrin PD solution remains stable for 336 hours (14 days) when refrigerated (4 degrees C) and for 168 hours (7 days) at room temperature (25 degrees C). Ceftazidime-icodextrin PD solution is stable for 168 hours and 48 hours, respectively, when stored at 4 degrees C and 25 degrees C. It is recommended that the bags be kept refrigerated whenever possible. Tobramycin-icodextrin solution stored at body temperature was stable up to 24 hours, and ceftazidime-icodextrin solutions up to 8 hours, permitting the practice of pre-warming solutions prior to administration.