Intravesical cytostatics: pH-dependence of antitumour activity

The effects of pH on the antitumour activity of six cytostatics--cisplatin, doxorubicin, ethoglucid, mitomycin C, thiotepa and VM-26--used in intravesical instillations were tested in vitro. The activity of cytostatics was determined on the Walker 256 carcinosarcoma cell line by using ATP-bioluminescence method. Cytostatics were incubated at different pH's (5.0-7.4) for 2 and 4 h. The activity of most of the cytostatics was not affected by pH, but mitomycin C had somewhat lower activity at pH 5.0 at 4 h and cisplatin at pH 6-7 at 2 and 4 h. Because the pH of normal urine is within the range used in this test, the use of a buffer solution during the intravesical instillation therapy is not necessary. However, according to our clinical experience, buffering is recommended to avoid chemical cystitis.