Stability of antibiotics in peritoneal dialysis fluids

Literature review A literature review of the stability of antibiotics in peritoneal dialysis fluids was conducted. The information obtained was collated and presented in a format which would serve as a useful working reference for hospital pharmacists. It was found that the stability of antibiotics in peritoneal dialysis fluids had received little attention in the literature. The review highlighted the lack of information on the stability and compatibility of many of the antibiotics and antibiotic combinations commonly used for the treatment of peritonitis. Despite increasing interest in intraperitoneal antifungal chemotherapy, there was no information on the stability of antifungal agents in peritoneal dialysis fluids. Stability studies A study of the stability of the antifungal agent, miconazole, in peritonealdialysis fluid was conducted. Greater than 10% loss of the initial miconazole concentration occurred within 4 hours when this drug was added to peritoneal dialysis fluid and stored in polyvinyl chloride (PVC) bags at 20°C. Similar admixtures were stable for at least 3 days when stored in glass ampoules under the same conditions. These findings indicated that the loss of miconazole observed in PVC bags was due primarily to an interaction with the container, rather than chemical decomposition in solution. Approximately 28% of the miconazole lost from the solution was recovered from the plastic by methanolic extraction, representing sorption of miconazole by the PVC container. In the clinicalsituation, the rapid loss of miconazole from peritoneal dialysis fluid stored in PVC bags, would demand that such admixtures be prepared immediately prior to administration. A study of the stability of both components of the antibacterial combination, co-trimoxazole, in peritoneal dialysis fluid was conducted. Greater than 10% loss of the initial trimethoprim concentration occurred within 3 days when admixtures of co-trimoxazole in peritoneal dialysis fluid were stored in PVC bags at 20°C. The concentration oftrimethoprim in similar admixtures stored in glass ampoules under the same conditions, remained virtually unchanged for 9 days. This suggested that the loss of trimethoprim observed in admixtures stored in PVC bags, may have been due to an interaction with the container. Greater than 10% loss of the initial sulphamethoxazole concentration occurred within 2 days in admixtures stored in PVC bags. Similar losses occurred in admixtures stored in glass ampoules, suggesting that the mechanism of this loss was primarily chemical decomposition in solution. Further evidence for this proposition, was the time dependent increase in concentration of an unknown decomposition product in admixtures stored in both plastic and glass containers. It was suspected that this compound was a derivative of sulphamethoxazole, however it was demonstrated that it was not sulphanilic acid or 5-methyl-3-isoxazolamine, which have previously been identified as decomposition products of sulphamethoxazole under acid conditions. This study found that the shelf-life of admixtures of co-trimoxazole in peritoneal dialysis fluid stored in PVC bags at 20°C, was limited by the stability of the sulphamethoxazole component. The data conservatively indicated a shelf-life of approximately 12 hours, since greater than 10% loss of the initialsulphamethoxazole concentration had occurred in this time in one of the admixtures examined.