DISEASE CHARACTERISTICS:

• Histologically confirmed solid tumor that is metastatic or unresectable and for which no standard curative or palliative measures exist or are effective
• No brain metastases or primary CNS malignancy

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• ECOG 0-2

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count at least 1,500/mm3
• Platelet count at least 100,000/mm3

Hepatic

• Bilirubin no greater than 1.5 mg/dL
• AST and ALT no greater than 3 times upper limit of normal

Renal

• Creatinine no greater than 1.5 mg/dL OR
• Creatinine clearance at least 60 mL/min

Cardiovascular

• No known active coronary artery disease

Pulmonary

• No pulmonary dysfunction

Other

• HIV negative
• No history of unusually severe and/or prolonged toxicity during prior therapy with fluorouracil (5-FU) or 5-FU prodrugs
• No diabetes mellitus requiring insulin or oral hypoglycemic therapy
• No ongoing or active infection requiring IV antibiotics
• No other serious concurrent medical illness that would preclude study
• No psychiatric illness or social situations that would preclude study
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy

• At least 4 weeks since prior immunotherapy and recovered
• No concurrent cytokines during the first course of therapy

Chemotherapy

• At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin) and recovered

Endocrine therapy

• No concurrent systemic corticosteroids

Radiotherapy

• At least 2 weeks since prior radiotherapy and recovered
• No prior pulmonary or mediastinal radiation exceeding 40 Gy

Surgery

• Recovered from prior surgery

Other

• No other concurrent investigational agents
• No concurrent cimetidine
• No concurrent sorivudine or brivudine