C. Joqueviel et al., URINARY STABILITY OF CARBOXYCYCLOPHOSPHAMIDE AND CARBOXYIFOSFAMIDE, 2MAJOR METABOLITES OF THE ANTICANCER DRUGS CYCLOPHOSPHAMIDE AND IFOSFAMIDE, Cancer chemotherapy and pharmacology, 40(5), 1997, pp. 391-399
Phosphorus-31 nuclear magnetic resonance spectroscopy was used to eval
uate the stability of carboxycyclophosphamide (CXCP) and carboxyifosfa
mide (CXIF) in human urine at pH 7.0 and 5.5 at 25 degrees, 8 degrees,
-20 degrees, and -80 degrees C. At 25 degrees C and pH 7.0, CXCP and
CXIF are relatively stable (approximate to 10% degradation in 24 h). I
n contrast, they are much less stable at pH 5.5 (approximate to 80% de
gradation of CXIF and approximate to 50% degradation of CXCP in 24 h).
The rate of degradation of CXCP and CXIF was a function of the storag
e temperature of the urine samples but, even at -80 degrees C, was not
negligible. approximate to 30% degradation for CXCP irrespective of p
H and approximate to 40% and 50% degradation for CXIF at pH 7.0 and 5.
5, respectively, after storage for 6 months. CXCP was more stable than
CXIF at either pH (7.0 or 5.5) and at all storage temperatures (8 deg
rees, -20 degrees, or -80 degrees C) of the urine samples. CXCP and CX
IF were more stable at pH 7.0 than at pH 5.5, although this difference
fell with decreasing temperatures to be almost negligible at -80 degr
ees C. To ensure a true estimate of CXCP and CXIF levels, urine sample
s must be frozen and stored at -80 degrees C within a few hours of mic
turition. CXCP and CXIF assays should also be carried out within 2 mon
ths and 1 month of storage, respectively.