Home Drug Guide Trastuzumab

Drug Guide

Generic Name

Trastuzumab

Brand Names Herceptin

Classification

Therapeutic: Antineoplastic agent, Monoclonal antibody

Pharmacological: HER2/neu receptor antagonist

FDA Approved Indications

HER2-positive breast cancer (adjuvant and metastatic)
HER2-positive gastric or gastroesophageal junction adenocarcinoma

Mechanism of Action

Trastuzumab is a monoclonal antibody that binds to the extracellular domain of the HER2 receptor, inhibiting the proliferation of tumor cells that overexpress HER2 and mediating antibody-dependent cellular cytotoxicity.

Dosage and Administration

Adult: Initial dose of 8 mg/kg IV infusion over 90 minutes, then 6 mg/kg every 3 weeks; may be given as a loading dose in certain regimens.

Pediatric: Not approved for pediatric use.

Geriatric: No specific dosage adjustment, but caution in elderly due to comorbidities.

Renal Impairment: No adjustment necessary.

Hepatic Impairment: No specific data; use caution.

Pharmacokinetics

Absorption: Administered intravenously, so bioavailability is 100%.

Distribution: Volume of distribution approximately 6-8 L.

Metabolism: Metabolized via proteolytic degradation into peptides and amino acids.

Excretion: Not renally excreted; degraded by proteolytic enzymes.

Half Life: Approximately 28.5 days (steady-state).

Contraindications

History of hypersensitivity to trastuzumab or its components.

Precautions

Left ventricular ejection fraction (LVEF) should be measured before and during treatment.
Use caution in patients with preexisting cardiomyopathy or who are receiving cardiotoxic chemotherapy.

Adverse Reactions - Common

Infusion reaction (Occasional)
Fatigue (Common)
Nausea (Common)
Diarrhea (Common)
Headache (Common)

Adverse Reactions - Serious

Cardiotoxicity, including CHF (Uncommon but serious)
Pulmonary toxicity including interstitial pneumonitis (Rare)
Infusion-related reactions possibly including hypotension, chills, fever, dyspnea (Uncommon)

Drug-Drug Interactions

Cardiotoxic agents such as anthracyclines may increase risk of cardiotoxicity.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Baseline cardiac function (LVEF), monitor for infusion reactions, signs of heart failure.

Diagnoses:

Risk for decreased cardiac output related to cardiotoxicity.

Implementation: Administer IV as prescribed, monitor cardiac status, be prepared to manage infusion reactions.

Evaluation: Assess for signs of cardiotoxicity, monitor LVEF periodically, evaluate tumor response.

Patient/Family Teaching

Report any symptoms of shortness of breath, fatigue, or swelling.
Inform about potential infusion reactions and need for monitoring.
Advise on avoiding pregnancy during and for at least 7 months after treatment.

Special Considerations

Black Box Warnings:

Cardiotoxicity, including HF and myocardial damage, which may be irreversible.

Genetic Factors: HER2 overexpression must be confirmed by testing before initiation.

Lab Test Interference: May cause falsely elevated levels of serum cardiac troponin and BNP.

Overdose Management

Signs/Symptoms: Severe infusion reactions, cardiomyopathy symptoms.

Treatment: Discontinue infusion, provide supportive care, follow cardiac function closely.

Storage and Handling

Storage: Store vials refrigerated at 2-8°C, protect from light.

Stability: Stable until expiration date on the label when stored properly.