Perjeta 420mg Injection is used to treat breast cancer. It belongs to group of medicine called monoclonal antibodies. Perjeta 420mg Injection is given as an injection into veins under the supervision of a doctor. 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. Hair loss, diarrhea, nausea, and fatigue are some common side effects of this medicine. This medicine may reduce the number of blood cells (decrease white blood cells) in your blood, thereby, increasing the susceptibility to infections. Regular blood tests are required to check your blood cells along with the heart, liver, and kidney. Many other medicines can affect, or be affected by, this medicine so let your healthcare team know all medications you are using. This medicine is not recommended during pregnancy or while breastfeeding. The use of effective contraception by both males and females during treatment is important to avoid pregnancy. "There is a Patient Support Program / Patient Assistance Program available in India for this medicine, being managed by Tata 1mg. Please contact your prescribing doctor to know more about the same. You may also call on (1800-102-1618) for more details."