Makindo Medical Notes

Always check the BNF here for up-to-date prescribing advice.

• Trastuzumab is a humanised monoclonal antibody targeting HER2/neu (ErbB2).
• Can be used as a single agent or in combination therapy (e.g. with paclitaxel) for HER2-positive breast cancer.
• Also indicated in other HER2-positive cancers (e.g. gastric cancer – see BNF).

⚙️ Mode of Action

• Binds tightly to the extracellular domain of the HER2 (ErbB2) receptor.
• Blocks downstream signalling ➝ inhibits proliferation of HER2-positive tumour cells.
• May also mediate antibody-dependent cell-mediated cytotoxicity (ADCC).

📋 Indications / Dose

• HER2-positive breast cancer (early and metastatic).
• HER2-positive gastric or gastro-oesophageal junction adenocarcinoma.
• Dose and schedule vary depending on indication and regimen (see BNF / chemotherapy protocols).

🔄 Interactions

• Refer to BNF for full details.
• Caution with other cardiotoxic agents (e.g. anthracyclines, cyclophosphamide).

⚠️ Cautions

• Monitor cardiac function (baseline & serial echocardiogram/MUGA scans).
• Increased risk of heart failure with prior anthracycline exposure.
• Infusion-related reactions more common with first dose.

⛔ Contraindications

• Severe cardiac impairment or symptomatic heart failure.
• Hypersensitivity to trastuzumab or excipients.
• See BNF for full contraindication list.

⚡ Side Effects

• Infusion reactions: fever, chills, nausea, dyspnoea, rash (especially with first infusion).
• Cardiotoxicity: left ventricular dysfunction, heart failure (higher risk with anthracyclines).
• GI upset: diarrhoea, vomiting.
• Respiratory: cough, dyspnoea (rare interstitial lung disease reported).
• Myelosuppression when combined with chemotherapy.

📚 References

• BNF – Trastuzumab
• EMA Summary of Product Characteristics (Herceptin®).
• National Cancer Institute – Trastuzumab.