Re-use of mitomycin C in the treatment of superficial tumours of the urinary bladder: an evaluation in view of its chemical stability.

The possibility of re-using mitomycin C (MMC) containing solutions after intravesical instillation in the urinary bladder is evaluated in view of the chemical stability of the drug. Generalized positive conclusions about the re-use of these solutions are unjustified due to the possible variation in the urinary pH of individual patients. Only in cases where the urinary pH during treatment is greater than 6 may re-use be considered, provided that bacterial contamination can be avoided. In cases where the pH is too low (i.e. less than 6) a considerable degradation occurs during instillation (about 34% at pH 5) and storage during 1 week at 4 degrees C (about 25% at pH 5). On the other hand, considering the acid activation pathway, induction of a low urinary pH during treatment might enhance the efficiency, although re-use in this case is impossible.