Mitomycin C resorption following repeated intravesical instillations using different instillation times.

In a prospective and randomized trial, 31 patients with superficial and/or CIS transitional cell carcinoma were treated by complete transurethral resection of all visible tumours, followed by instillation of 40 mg mitomycin C (MMC). The instillation time was 0.5 and 1.0 h. The resorption of MMC by the bladder wall was not influenced by the instillation time. There was no cumulative effect on MMC resorption observed in consecutive instillations. Less than 1% of the instilled dose of MMC was resorbed. The maximum plasma concentration of MMC never exceeded 31 ng/ml. After instillation, mean percentages of MMC found in urine were 40.3 (0.5 h group) and 46.4 (1.0 h group), respectively. The only side-effects observed were chemical cystitis, contact and general exanthema. The instillation time had no influence on these side-effects. Bone marrow toxicity has not been observed.