Intravesical chemotherapy. Studies on the relationship between pH and cytotoxicity

The influence of pH on the antitumor activity of drugs used for intravesical chemotherapy was studied. A human continuous cell line derived from a transitional cell carcinoma of the bladder was exposed to 6 drugs (Adriamycin [doxorubicin], cisplatin, epirubicin, epodyl, mitomycin C, and thiotepa) for 1 hour at 11 pH values ranging from 5.2 to 9.7, and cytotoxicity was measured by inhibition of colony formation. pH had a marked influence on drug activity: cisplatin, mitomycin C, and thiotepa were most cytotoxic in acid media, Adriamycin, and epirubicin in alkaline media, while epodyl was the only drug whose cytotoxicity was unaffected by pH. In addition to these in vitro studies, comparisons were made of the pH of urine samples obtained from patients immediately before and at the completion of intravesical chemotherapy. Changes in pH up to a maximum of +/- 1.6 units were observed, although in most cases, values were similar before and after therapy. All the drugs used were acidic in solution, with the exception of thiotepa. It is concluded that by adjusting solvent and urine pH to the optimum value for each drug, the effectiveness of intravesical chemotherapy might be enhanced.