Anti-HER2 monoclonal antibody

Trastuzumab (Specialist drug)

Brand names: Herceptin, Herzuma, Ontruzant

Trastuzumab is a monoclonal antibody used under specialist supervision for HER2-positive breast cancer and HER2-positive metastatic gastric cancer.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It binds the HER2 receptor on tumour cells, blocking HER2-mediated growth signalling and recruiting immune-mediated cytotoxicity.

Prescribing in practice

Cardiotoxicity is the key concern — assess cardiac function before and during treatment and avoid or use cautiously with anthracyclines.
It is reserved for HER2-positive tumours confirmed by validated testing and is prescribed by oncology specialists.
Infusion-related reactions can occur, particularly with the first infusion.

Monitoring

Monitor left ventricular ejection fraction at baseline and at regular intervals throughout therapy.

Counselling the patient

Report breathlessness, ankle swelling, palpitations or a persistent cough.
Tell the team about any reaction during or shortly after an infusion.
Effective contraception is advised during and after treatment.

Evidence & guidelines

Benefit in HER2-positive breast cancer is established by the HERA and pivotal adjuvant trials and supported by NICE guidance.

Reference: NICE TA34/TA208; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways