Herceptin is known generically as trastuzumab. It has the ability to treat some breast cancers. Its adverse effects include anemia, etc. It should be used with caution. Trastuzumab has a role in the treatment of HER2-positive early breast cancer, unresectable or locally metastatic HER2-positive advanced breast cancer. Before using the drug, pathological and genetic tests are required to clarify the presence of therapeutic targets. The drug is contraindicated in case of drug allergy. The drug needs to be used to stop breastfeeding and avoid pregnancy until seven months after stopping the drug. The use of the drug must be monitored by an experienced clinician, and the drug needs to be permanently discontinued in the event of serious adverse reactions such as interstitial lung disease, congestive heart failure, and severe hepatic impairment. Adverse reactions such as anemia, insomnia, headache, and bleeding can be intervened by symptomatic treatment or dosage adjustment. Please use trastuzumab under the supervision of a physician, unauthorized use of the drug is absolutely prohibited.