DISEASE CHARACTERISTICS: Histologically or cytologically confirmed solid tumor not amenable to standard therapy No brain tumor involvement or leptomeningeal disease

PATIENT CHARACTERISTICS: Age: 18 to 70 Performance status: WHO 0-2 Life expectancy: At least 3 months Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin less than 1.5 mg/dL Transaminases and alkaline phosphatase no greater than 2.5 times upper limit of normal (ULN) (no greater than 5 times ULN for liver metastases) Renal: Creatinine no greater than 1.4 mg/dL OR Creatinine clearance at least 60 mL/min Other: No active bacterial infections (e.g., abscess or fistula) No other nonmalignant disease that precludes protocol therapy No history of alcoholism, drug addiction, or psychotic disorders that would prevent compliance No glaucoma Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior immunotherapy Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas) Endocrine therapy: At least 4 weeks since prior anticancer hormonal therapy Radiotherapy: At least 4 weeks since prior radiotherapy (6 weeks for extensive radiotherapy) No concurrent radiotherapy except for localized palliation Surgery: Not specified Other: No other concurrent investigational drugs or antitumor drugs No sulphonylureas or anti-arrhythmic agents