Trastuzumab and hyaluronidase-oysk injection is used along with other medications or after other medications have already been used to treat a certain type of breast cancer that has spread to other parts of the body. Trastuzumab and hyaluronidase-oysk injection is also used during and after treatment with other medications to decrease the chance that a certain type of breast cancer will return. Trastuzumab and hyaluronidase-oysk injection is in a class of medications called monoclonal antibodies. It works by stopping the growth of cancer cells.

Trastuzumab and hyaluronidase-oysk injection may cause serious or life-threatening heart problems. Tell your doctor if you have or have ever had heart disease. Your doctor will order tests before and during your treatment to see if your heart is working well enough for you to safely receive trastuzumab and hyaluronidase-oysk injection. Tell your doctor and pharmacist if you are being treated with anthracycline medications for cancer such as daunorubicin (Cerubidine), doxorubicin (Doxil), epirubicin (Ellence), and idarubicin (Idamycin). Your doctor will need to monitor you closely if you receive these medications during your treatment with trastuzumab and hyaluronidase-oysk injection and for up to 7 months after your final dose. If you experience any of the following symptoms, call your doctor immediately: cough; shortness of breath; swelling of the arms, hands, feet, ankles or lower legs; weight gain (more than 5 pounds [about 2.3 kilograms] in 24 hours); dizziness; loss of consciousness; or fast, irregular, or pounding heartbeat.

Trastuzumab and hyaluronidase-oysk injection may cause serious or life-threatening reactions that may occur while the medication is being given or up to 24 hours after a dose. Trastuzumab and hyaluronidase-oysk injection may also cause severe lung damage. Tell your doctor if you have or have ever had lung disease or if you have a tumor in your lungs, especially if it has caused you to have difficulty breathing. Your doctor will watch you carefully when you receive trastuzumab and hyaluronidase-oysk injection so that your treatment can be interrupted if you experience a serious reaction. If you have any of the following symptoms, tell your doctor immediately: fever; chills; nausea; vomiting; diarrhea; chest pain; headache; dizziness; weakness; rash; hives; itching; swelling of the face, eyes, mouth, throat, tongue, or lips; or difficulty breathing or swallowing.

Tell your doctor if you are pregnant or plan to become pregnant. Trastuzumab and hyaluronidase-oysk injection may harm your unborn baby. You should use birth control to prevent pregnancy during your treatment and for 7 months after your final dose. Talk to your doctor about birth control methods that will work for you. If you become pregnant during your treatment with trastuzumab and hyaluronidase-oysk injection, call your doctor immediately.

Keep all appointments with your doctor and the laboratory. Your doctor will order certain tests to check your body's response to trastuzumab and hyaluronidase-oysk injection.

Talk to your doctor about the risks of receiving trastuzumab and hyaluronidase-oysk injection.

Trastuzumab and hyaluronidase-oysk injection comes as a liquid to be injected under the skin in the thigh over 2 to 5 minutes. Trastuzumab and hyaluronidase-oysk injection is given by a doctor or nurse in a hospital or medical facility. It is usually given once every 3 weeks. The length of your treatment will depend on the condition that you have and how well your body responds to treatment.

Before receiving trastuzumab and hyaluronidase-oysk injection,

• tell your doctor and pharmacist if you are allergic to trastuzumab, hyaluronidase (Amphadase, Vitrase), any other medications, or any of the ingredients in trastuzumab and hyaluronidase-oysk injection.
• tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention the medications listed in the IMPORTANT WARNING section, especially if you receive them within 7 months after stopping trastuzumab and hyaluronidase-oysk injection. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had any of the conditions mentioned in the IMPORTANT WARNING section or any other medical condition.
• tell your doctor if you are breastfeeding.
• if you are having surgery, including dental surgery, tell the doctor or dentist that you are receiving trastuzumab and hyaluronidase-oysk injection.

Call your doctor right away if you are unable to keep an appointment to receive a dose of trastuzumab and hyaluronidase-oysk injection.

Unless your doctor tells you otherwise, continue your normal diet.

Trastuzumab and hyaluronidase-oysk injection may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

• diarrhea
• constipation
• stomach pain
• heartburn
• loss of appetite
• changes in taste
• mouth sores
• arm, leg, back, bone, joint, or muscle pain
• pain or redness in the area where the medication was injected
• hair loss
• difficulty falling asleep or staying asleep
• hot flashes
• numbness, burning, or tingling in the arms, hands, feet, or legs
• changes in the appearance of nails
• acne
• depression

Some side effects can be serious. If you experience any of these symptoms or those listed in the IMPORTANT WARNING section, call your doctor immediately:

• sore throat, fever, chills, difficult or painful urination, and other signs of infection
• nosebleeds or other unusual bruising or bleeding
• excessive tiredness
• pale skin
• nausea; vomiting; loss of appetite; fatigue; rapid heartbeat; dark urine; decreased amount of urine; stomach pain; seizures; hallucinations; or muscle cramps and spasms

Trastuzumab and hyaluronidase-oysk injection may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

Ask your pharmacist any questions you have about trastuzumab and hyaluronidase-oysk injection.

Your doctor will order a lab test before you begin your treatment to see whether your cancer can be treated with trastuzumab and hyaluronidase-oysk.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

• Herceptin Hylecta®