Trastuzumab belongs to the group of cancer-fighting medications known as antineoplastics, and in particular to the family of medications known as monoclonal antibodies. It is used in addition to other therapies to treat early stage breast cancer and metastatic (cancer that has spread) breast cancer that produce a substance known as HER2 protein. The intravenous (into a vein) form of trastuzumab  is also used in combination with other medications to treat metastatic stomach cancer that produces the HER2 protein. Trastuzumab fights these cancers by seeking out and killing the specific types of cancer cells that carry this protein.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are receiving this medication, speak to your doctor.

The recommended dose and dosing schedule of trastuzumab varies according to body size and the type of cancer. It is injected into a vein through a specially prepared site on your skin over 90 minutes. The medication may be injected over 30 minutes if previous doses were tolerated well.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are receiving this medication without consulting your doctor.

Very careful handling of this medication is required. It is always given under the supervision of a doctor in a hospital or similar setting with access to sterile equipment for preparation.

Trastuzumab can cause a number of side effects. It may cause nausea and vomiting, but medications can be given to control this. Your doctor, nurse, or pharmacist can advise you on how to reduce the effects of nausea and vomiting. Keep track of any side effects and report them to your doctor as suggested in the section, "What side effects are possible with this medication?"

It is important this medication be given exactly as recommended by your doctor. If you miss an appointment to receive trastuzumab, contact your doctor as soon as possible to reschedule your appointment.

This medication is stored in the refrigerator.

Each vial of sterile, white-to-pale-yellow lyophilized powder for IV administration, under vacuum, contains 440 mg of trastuzumab. Nonmedicinal ingredients: 400 mg of α,α-trehalose dihydrate, 9.9 mg of L-histidine HCl, 6.4 mg of L-histidine, and 1.8 mg of polysorbate 20. Preservative-free. Bacteriostatic water for injection supplied as a 20 mL vial of sterile solution containing 1.1% benzyl alcohol (as antimicrobial preservative), yields 21 mL of a multi-dose solution containing 21 mg/mL of trastuzumab.

Trastuzumab should not be used by anyone who is allergic to trastuzumab, murine proteins, Chinese hamster ovary (CHO) cell proteins, or to any of the ingredients of the medication.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who receives this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people receiving this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• appetite loss
• changes in nails
• constipation
• cough
• fatigue
• fever and chills
• headache
• mild diarrhea
• nausea
• pain (e.g., muscle and joint pain)
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• diarrhea (more than 4 extra bowel movements a day or any at night)
• fast heartbeat
• itching
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don’t stop bleeding)
• symptoms of an infusion reaction (e.g., itching, wheezing, dizziness, fast heart rate)
• symptoms of anemia (e.g., shortness of breath, tiredness, fast heart rate)
• symptoms of heart problems (e.g., swelling of feet or lower legs, shortness of breath)
• symptoms of infection (e.g., fever or chills, sore throat, cough, redness or swelling, painful urination)
• symptoms of kidney problems (e.g., decreased urine production; drowsiness; shortness of breath; fatigue; swelling of the legs, ankles, or feet)
• symptoms of lung problems (e.g., shortness of breath, wheezing, or coughing)
• trouble swallowing

Seek immediate medical attention if any of the following occur:

• chest pain
• shortness of breath
• symptoms of an allergic reaction (e.g., hives; dizziness; fast heart rate; difficulty breathing; swelling of the lips, tongue, or throat)
• wheezing

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Allergic reactions: This medication may cause an allergic reaction (e.g., dizziness; hives; fast heart rate; swelling of the lips, tongue, or throat). If you experience these symptoms, tell your doctor immediately.

Drowsiness/reduced alertness: Trastuzumab may cause drowsiness or dizziness, affecting your ability to drive or operate machinery. Avoid driving, operating machinery, or performing other potentially hazardous tasks until you have determined how you are affected by this medication.

Heart disease: This medication can cause heart problems such as heart failure. People with heart disease are more at risk for these problems. Your doctor will perform tests at regular intervals to monitor for any changes in your heart function. If you experience symptoms of heart function changes such as shortness of breath, worsening cough, difficulty breathing at night, swelling of the feet or hands, contact your doctor immediately.

Infection: As well as killing cancer cells, this medication can reduce the number of cells that fight infection in the body (white blood cells). Avoid contact with people who have contagious infections and tell your doctor if you begin to notice signs of an infection, such as fever or chills.

Infusion reactions: This medication can cause reactions that are related to the infusion. Symptoms of a reaction include itching, dizziness, wheezing, fast heart rate, difficulty breathing, and a dramatic drop in blood pressure. The reaction does not usually last very long, but may need to be treated as it can cause death if it is severe. The reaction usually occurs during or shortly after receiving the medication, but can also be delayed. If you experience symptoms of an infusion reaction, let your nurse or doctor know immediately or get immediate medical attention.

Lung problems: This medication can cause lung problems, especially for people with lung disease or lung cancer, or who have received or are receiving other anticancer medications or radiation therapy. Let your doctor know immediately if you begin to experience shortness of breath or persistent cough.

Preservative: The intravenous form of this medication contains benzyl alcohol, which acts as a preservative. Inform a member of your health care team if you have had a previous reaction to benzyl alcohol.

Pregnancy: This medication can cause harm to the fetus if used during pregnancy. People who could become pregnant should use effective contraception while receiving this medication and for 7 months after stopping it. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if trastuzumab passes into breast milk. If you are breast-feeding and receiving this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: Seniors may be more at risk for experiencing certain side effects from this medication.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.