HERCEPTIN 440mg INFUSION is used in the treatment of breast and stomach cancer. It works by killing the cancer cells by inhibiting HER2 (human epidermal growth factor receptor protein). HERCEPTIN 440mg INFUSION is given as an injection by a qualified medical professional. Your doctor will decide what dose is necessary and how often you need to take it. This will depend on what you are being treated for and may change from time to time. You should take it exactly as your doctor has advised. Taking it in the wrong way or taking too much can cause very serious side effects. It may take several weeks or months for you to see or feel the benefits but do not stop taking it unless your doctor tells you to.