trastuzumab, Herceptin

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GENERIC NAME: trastuzumab

BRAND NAME: Herceptin

DRUG CLASS AND MECHANISM: Trastuzumab is an intravenous drug that is used to treat breast cancer that has spread beyond the breast (metastasized). It belongs to a class of drugs called monoclonal antibodies. Other monoclonal antibodies include rituximab (Rituxan) and gemtuzumab ozogamicin (Mylotarg). The cells of cancers have various receptors on their surfaces. Chemicals bind to these receptors and cause changes within the cancer cells. One of the receptors that occurs in about one-third of all breast cancers is called HER2. HER2 is known to control the growth and development of the cancer cells and the production of new cancer cells. If HER2 receptors are present in large numbers on the cancer cells (often referred to as overexpression of HER2), then the cancer cells may multiply and grow quickly. Normally, the immune system produces antibodies that will detect and attack HER2 receptors to slow the growth of cancer cells However, if HER2 is present in large numbers, the immune system may be unable to control HER2. Trastuzumab is a man-made antibody developed using molecular cloning and recombinant DNA technology. Trastuzumab is thought to block the HER2 receptors when there is overexpression, thereby blocking growth of the cancer . Trastuzumab was approved by the FDA in 1998.



PREPARATIONS: Trastuzumab is available as a powder in a vial containing 440 mg of drug. It must be mixed with a liquid before intravenous injection.

STORAGE: Trastuzumab should be stored at 2 C to 8 C (36 F to 46 F) and should not be frozen.

PRESCRIBED FOR: Trastuzumab is used to treat metastatic breast cancer or metastatic gastric or gastroesophageal junction adenocarcinoma among patients who overexpress HER2. It may be used alone or combined with other chemotherapeutic drugs.

DOSING: Trastuzumab is administered intravenously. When combined with other drugs for treatment of breast cancer the dose is 4 mg per kilogram of body weight followed by a weekly dose of 2 mg per kilogram of body weight. When used alone for treatment of breast cancer or for treatment of gastric cancer the dose is 8 mg/kg initially followed by 6 mg/kg every 3 weeks.

DRUG INTERACTIONS: Paclitaxel may increase blood levels of trastuzumab.

PREGNANCY: Trastuzumab can cause fetal harm when administered to pregnant women and should not be administered during pregnancy.

NURSING MOTHERS: It is not known whether trastuzumab is excreted in human milk. Nursing mothers should decide whether to stop nursing or discontinue trastuzumab.

SIDE EFFECTS: The most common side effects of trastuzumab are diarrhea (25% of patients), a prickling or burning sensation in the skin (9% of patients), either an upper respiratory or a catheter related infection (26% of patients), increased cough (26% of patients), nausea and vomiting (23-33% of patients), rash (18% of patients), and infusion related side effects including mild to moderate chills and/or fever (40% of patients). More patients experience these side effects when trastuzumab is given in combination with paclitaxel. Back pain may occur in 22% of patients receiving trastuzumab alone. More serious but less-common side effects may develop if trastuzumab is given with paclitaxel and other chemotherapeutic drugs, for example, cyclophosphamide (Cytoxan) or doxorubicin (Rubex). Damage to the heart including congestive heart failure (CHF) or ventricular dysfunction may occur in 19% of patients receiving trastuzumab with another chemotherapeutic drug in contrast to 2% to 20% of patients receiving only one of the drugs. Trastuzumab also causes serious and fatal pulmonary toxicity. Other less-common side effects of trastuzumab alone or combined with paclitaxel include decreased red and/or white blood cells, increased heart rate, body swelling, acne, and herpes simplex infections.

Reference: FDA Prescribing Information

Medically Reviewed by a Doctor on 3/6/2013

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