Irreversible myocardial toxicity, including life-threatening or fatal CHF, may occur during therapy or months to years after termination of therapy. Risk of developing CHF increases rapidly with increasing total cumulative dosages ≥450 mg/m^2^. Risk of cardiotoxicity (may occur at lower cumulative dosages and may develop long after discontinuance of therapy). Total dosage administered to patient should take into account previous or concomitant therapy with related agents (e.g. daunorubicin, idarubicin, mitoxantrone). Children are at increased risk for developing delayed cardiotoxicity; myocardial growth may be impaired as pediatric patients mature, leading to possible development of CHF during early adulthood. Acute life-threatening arrhythmias reported during or within a few hours after administration. Neutropenia, leukopenia (granulocytopenia), thrombocytopenia and anemia may occur. Contraindicated in marked pre-existing myelosuppression. May potentiate toxicity of other antineoplastic agents. Extravasation produces severe local tissue necrosis (may result in limitation of mobility of adjacent joints). Phlebosclerosis may occur, especially when drug is administered into small vein or repeatedly into a single vein. Serious and sometimes life-threatening or fatal allergic/anaphylactoid-like infusion reactions reported with liposomal doxorubicin. Therapeutic response is not likely to occur without some evidence of toxicity (e.g. effects on bone marrow, GI and oral mucosa, hair follicles). Tumor lysis syndrome and hyperuricemia may result from extensive purine catabolism (in rapidly growing tumors). Mutagenic and carcinogenic in experimental models. Treatment-related AML reported in patients receiving doxorubicin-containing adjuvant chemotherapy regimens. Risk of developing secondary AML and other neoplasms is increased in pediatric patients receiving doxorubicin or other topoisomerase II inhibitors. Use with caution in hepatic impairment (possible increased toxicity if given at usual recommended dosages). Use with caution in hepatobiliary dysfunction. Use with caution in patients who have received radiation therapy. Administration of live vaccines to immunosuppressed patients may be hazardous.