DISEASE CHARACTERISTICS:

• Histologically confirmed transitional cell carcinoma (TCC) of the urothelium, including the bladder, renal pelvis, ureter, and urethra

  • Stage T2-4, N0-3, M1 OR stage T2-4, N+, M0, unresectable disease

  • The following additional histologic subtypes are eligible:

    • Poorly differentiated TCC
    • Predominant TCC with rare foci of squamous differentiation
    • Predominant TCC with rare foci of adenocarcinoma

  • The following histologic subtypes are ineligible:

    • Adenocarcinoma
    • Small cell carcinoma
    • Sarcoma
    • Squamous cell carcinoma
    • Mixed adeno/squamous/transitional histology
• Incurable by surgery or radiotherapy
• Progressed or recurred after 1, and only 1, prior cisplatin- or carboplatin-containing systemic regimen for metastatic disease

• Measurable disease

  • Soft tissue disease that has been irradiated within the past 2 months is not considered measurable disease

• No uncontrolled CNS metastases

  • CNS metastases that have responded to or stabilized after prior radiotherapy are allowed

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Zubrod 0-2

Life expectancy

• Not specified

Hematopoietic

• Absolute granulocyte count at least 1,200/mm^3
• Platelet count at least 100,000/mm^3

Hepatic

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• SGOT less than 3 times ULN (5 times ULN if liver metastases are present)

Renal

• Creatinine less than 2 times ULN

Other

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or adequately treated stage I or II cancer that is currently in complete remission

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• See Disease Characteristics
• At least 28 days since prior chemotherapy
• No prior topoisomerase I inhibitors (e.g., irinotecan or topotecan)

Endocrine therapy

• Not specified

Radiotherapy

• See Disease Characteristics
• At least 28 days since prior radiotherapy to the pelvis

Surgery

• Not specified

Other

• Recovered from prior therapy
• Prior adjuvant therapy allowed
• At least 14 days since prior Hypericum perforatum (St. John's Wort)
• More than 7 days since prior phenytoin, phenobarbital, carbamazepine, or any other enzyme-inducing anticonvulsant drugs (EIACDs)
• No St. John's Wort during and for 7 days after study participation
• No concurrent EIACDs
• No concurrent myelosuppressants
• No concurrent medications that cause diarrhea
• Concurrent gabapentin or other non-EIACDs are allowed