Pazopanib Hydrochloride in Treating Patients With Metastatic Urethral Cancer or Bladder Cancer That Has Relapsed or Not Responded to Treatment

DISEASE CHARACTERISTICS: * Histologically confirmed diagnosis of transitional cell tumors of the bladder or the urothelium * Metastatic disease * Relapsed or refractory disease * Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 2 cm by conventional techniques or ≥ 1 cm by spiral CT scan * Must have failed ≥ 1 cisplatin-based conventional chemotherapy regimen for metastatic disease (neoadjuvant/adjuvant therapy excluded) * No history or clinical evidence of CNS metastases or leptomeningeal carcinomatosis, except for individuals who were previously treated for CNS metastases, are asymptomatic, and have had no requirement for steroids or anti-seizure medication for the past 6 months PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Life expectancy ≥ 12 weeks * Hemoglobin ≥ 9.0 g/dL * Absolute neutrophil count ≥ 1,000/μL * Platelet count ≥ 75,000/μL * Total bilirubin ≤ 1.5 x upper limit of normal (ULN) * ALT and AST ≤ 2.5 x ULN (≤ 5 x ULN for patients with liver involvement) * Alkaline phosphatase ≤ 4 x ULN * Serum creatinine ≤ 1.5 mg/dL * PT-INR/PTT \< 1.5 x ULN * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective barrier contraception during and for 3 months after completion of study therapy * Able to swallow oral medication * None of the following cardiovascular conditions within the past 6 months: * Cardiac angioplasty or stenting * Myocardial infarction * Unstable angina * Symptomatic peripheral vascular disease * NYHA class III or IV congestive heart failure * Cardiac arrhythmias requiring anti-arrhythmic therapy (beta-blockers or digoxin are permitted) * Uncontrolled hypertension * No history of HIV infection or active chronic hepatitis B or C * No active clinically serious infections \> grade 2 NCI-CTC version 4.0 * No seizure disorder requiring medication (e.g., steroids or anti-epileptics) * No history of any of the following conditions within the past 6 months: * Cerebrovascular accident * Pulmonary embolism * Untreated deep venous thrombosis * No evidence or history of bleeding diathesis * No known endobronchial lesions or involvement of large pulmonary vessels by tumor * No hemoptysis within the past 6 weeks * No gastrointestinal abnormalities that may increase the risk of GI bleeding or affect the absorption of investigational study drug * No other cancer that is distinct in primary site or histology from the cancer being evaluated in this study, except cervical carcinoma in situ, treated basal cell carcinoma, or any cancer curatively treated \> 5 years prior to study entry * No substance abuse, medical, psychological, or social conditions that may interfere with the study participation or evaluation of the study results * No concurrent unstable condition that could jeopardize patient safety and their compliance in the study * No non-healing wound, fracture, or ulcer within the past 28 days * No major trauma within the past 28 days * No known immediate or delayed hypersensitivity reaction or idiosyncrasy to drugs chemically related to pazopanib hydrochloride PRIOR CONCURRENT THERAPY: * See Disease Characteristics * Recovered from all prior therapy * At least 14 days since prior radiotherapy, except palliative radiotherapy * At least 14 days since tumor embolization * At least 14 days or 5 half-lives (whichever is longer) of a drug since prior chemotherapy, immunotherapy, biologic therapy, investigational therapy, or hormonal therapy * At least 3 weeks since prior biologic response modifiers (e.g., G-CSF) * G-CSF and other hematopoietic growth factors may be used in the management of acute toxicity (e.g., febrile neutropenia) when clinically indicated or at the discretion of the investigator, however they may not be used to avoid a required dose reduction * Chronic erythropoietin allowed provided no dose adjustment is undertaken within 2 months prior to the study or during the study * No prior pazopanib hydrochloride * No coronary artery by-pass graft surgery within the past 6 months * No major surgery within the past 28 days * Concurrent coumadin or heparin for therapeutic anticoagulation allowed provided that no prior evidence of underlying abnormality in PT-INR/PTT parameters exist * Not concurrently undergoing renal dialysis