DISEASE CHARACTERISTICS: Histologically proven relapsed or incurable solid tumors No primary or metastatic CNS disease

PATIENT CHARACTERISTICS: See General Eligibility Criteria

PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: At least 3 weeks since prior cytotoxic chemotherapy (6 weeks since prior mitomycin or nitrosourea) Prior doxorubicin HCl allowed (no extensive therapy) Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: Prior surgery allowed Other: Recovered from toxic effects of prior therapy At least 4 weeks since prior investigational or approved clinical trial agents No concurrent cimetidine, phenothiazines, phenytoin, calcium channel blockers, or cyclosporine or other P-glycoprotein inhibitors --Patients Characteristics-- Age: 18 and over Performance Status: Karnofsky 70-100% Life Expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Hemoglobin at least 9.0 g/dL Platelet count at least 100,000/mm3 Hepatic: AST and/or ALT no greater than 2 times upper limit of normal Bilirubin normal Renal: Creatinine normal Creatinine clearance at least 60 mL/min Cardiovascular: No clinically significant EKG abnormalities No atrial or ventricular arrhythmias requiring medication No ischemic event within 6 months of study Cardiac ejection fraction at least 50% by MUGA scan Other: Not pregnant or nursing Fertile patients must use effective contraception No prior or concurrent seizure disorders No prior or concurrent clinically significant medical illness No known hypersensitivity to doxorubicin HCl or other study medications No other active malignancies except curatively treated carcinoma in situ of the cervix or basal cell skin cancer