Pertuzumab side effects: the complete list and timeline

Pertuzumab is almost always given with trastuzumab, and at the start usually with chemotherapy, so the side effects you notice come from the whole combination rather than pertuzumab alone. The side effect that pertuzumab adds most clearly is loose motions, or diarrhoea. It is very common in the months when chemotherapy is given too, usually mild to moderate, and often starts within the first cycle. It tends to settle once chemotherapy stops, although some people have milder loose motions for as long as they take the antibodies. Skin rash, dry skin, itching and nail changes are also more common with pertuzumab. Hair loss, low white cell counts, tiredness, feeling sick, mouth sores and tingling or numbness in the hands and feet mostly come from the chemotherapy given alongside, and usually ease after it ends. Reactions during the drip, such as chills or fever, are most likely with the first dose. The side effect that needs regular checking is a fall in the heart's pumping strength. It is uncommon, usually causes no symptoms, and is found through routine heart scans; with a pause in treatment and heart medicines it often improves. Pertuzumab can harm an unborn baby, so effective contraception is needed during treatment and for several months after the last dose. Most people complete their planned course with the help of simple supportive treatment.

Loose motions are the signature effect

Diarrhoea is the side effect most linked to adding pertuzumab, especially during chemotherapy.

Many effects belong to chemotherapy

Hair loss, low blood counts and tingling mainly come from the chemotherapy and fade after it ends.

The heart is checked regularly

Scans before and during treatment pick up changes early, usually before any symptoms appear.

A list of side effects describes what can happen across many people. It does not predict what will happen to you, and most people have only some of them.

Blame is hard to assign

Because pertuzumab is given with other treatments, it is not always possible to say which medicine caused a particular problem. Your team judges this from the timing and pattern.

Some effects last longer

Tingling in the hands and feet from chemotherapy can take months to improve and occasionally does not settle fully.

Rare problems exist

Serious allergic reactions, severe diarrhoea with dehydration and heart failure are uncommon, but they can happen and need prompt care.

What this page cannot tell you

It cannot tell you which side effects you will have or how strongly. Your oncologist and nurses can explain your personal risks based on your plan and health.

Some symptoms need same-day advice. Keep your treatment unit's emergency number where your family can find it.

Fever or shivering

A temperature of thirty-eight degrees or above, or feeling shivery and unwell, especially in the weeks when chemotherapy is given, needs urgent assessment.

Severe or persistent diarrhoea

Loose motions many times a day, diarrhoea at night, blood in the stool, or dizziness from fluid loss should be reported straight away.

Heart warning signs

New breathlessness, needing extra pillows at night, swollen ankles or a pounding heartbeat should be checked promptly.