What is the primary toxicity of doxorubicin (Adriamycin)?

Doxorubicin, an antibiotic derived from Streptomyces species, has activity against sarcomas and carcinomas of the breast, liver, bladder, prostate, head and neck, esophagus, and lung. Its major side effect is production of a dilated cardiomyopathy. Patients receiving this agent should have echocardiography before and after treatment in order to monitor potential cardiac toxicity.