The stability of ifosfamide in aqueous solution and its suitability for continuous 7-day infusion by ambulatory pump

Dose fractionation is known to reduce the toxicity of ifosfamide and also results in an increased production of alkylating metabolites. Administration by slow infusion using the convenience of ambulatory pumps is therefore of interest. We used HPLC to investigate the stability of ifosfamide in aqueous solution (either alone, solution A, or mixed with mesna, solution B) under various conditions over a 9-day period. At both ambient temperature in daylight and 27 degrees C in a dark environment, there was no evidence of ifosfamide decay in either solution. However, at 37 degrees C in a dark environment, a fall was detected in both solutions, which at 9 days amounted to a loss of 7% of the amount of ifosfamide present at time zero. At 70 degrees C, levels of ifosfamide in both solutions fell within 72 h to markedly lower levels than controls, thus confirming that the methods used were indicative of stability. We conclude that ifosfamide, either alone or mixed with mesna, is stable for 9 days at temperatures up to 27 degrees C; even at 37 degrees C, the measured loss is small. The continuous infusion of ifosfamide over 7 days by ambulatory pump is now a practical proposition.