Blocks a specific target (a lock) on the cancer cells, so it mainly affects cells with that target.
The medicines
Tap the side effect you have on the map to see how severe it is and what to do. Not everyone gets every side effect, and most are mild.
From: Trastuzumab
Tired, better with rest
Manage at home
Mild (grade 1)
Tired, but better with rest.
Moderate (grade 2)
Not better with rest; you cannot do housework, shopping or work as usual.
Severe (grade 3 or 4)
Cannot get out of bed or walk, fainting, dizziness on standing, or tiredness with breathlessness or confusion.
From: Trastuzumab
Some medicines can cause a reaction while being given: flushing, rash, breathlessness, chest tightness or back pain.
When: During or soon after the drip, most often the first or second time.
What helps:
Uncommon but important. We look for these with blood tests, an ECG or scans.
From: Trastuzumab
Some medicines can weaken the heart muscle or affect its rhythm.
When: Can happen during or after treatment.
What helps:
Check your symptoms in My treatment
General information. Doses are not shown. Your own doctor may advise differently. When to seek help urgently
Written and medically reviewed by Dr Prathyusha Eaga, MD, DM (Medical Oncology). Last reviewed: 12 October 2026. Based on NCCN and ESMO guidelines.
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