Aminopterin in Treating Patients With Refractory Leukemia

DISEASE CHARACTERISTICS: Histologically proven acute leukemia of any histologic type that is refractory to known effective therapy

PATIENT CHARACTERISTICS: Age: Any age Performance status: Karnofsky 50-100% Life expectancy: At least 6 weeks Hematopoietic: Not specified Hepatic: Bilirubin no greater than 1.5 mg/dL ALT no greater than 5 times upper limit of normal Renal: Creatinine normal for age Cardiovascular: No unstable angina No uncontrolled arrhythmia Pulmonary: No third space effusion Other: No severe uncontrolled infection Adequate nutritional status At least third percentile for weight Normal total serum protein Normal albumin/globulin ratio No serious concurrent physical or mental illness Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 3 months since prior bone marrow transplantation Recovered from prior biologic therapy No concurrent anticancer biologic therapy Chemotherapy: Recovered from prior chemotherapy No concurrent anticancer chemotherapy Endocrine therapy: Recovered from prior endocrine therapy No concurrent anticancer endocrine therapy No concurrent dexamethasone or other steroids as antiemetic agents Radiotherapy: No concurrent anticancer radiotherapy Surgery: Not specified Other: No concurrent dairy products for 2-4 hours before, during, or 2-4 hours after study drug No concurrent trimethoprim-sulfamethoxazole or dapsone as prophylaxis for Pneumocystis infection No concurrent multivitamins containing folic acid