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Pertuzumab/Trastuzumab (Phesgo®)

Q: What Precautions Should I Take When Taking Or Using This Medication?

Inform your healthcare professional if: You are allergic to this medication or any of the other ingredients of this medication. You are taking any other medications, including supplements, traditional medications and herbal remedies. You have any other medical conditions. You are going to receive any vaccination or surgery, including dental surgery. You have any plans to start a family in the future. Pertuzumab/Trastuzumab may have an anti-fertility effect, which could be irreversible. You should discuss fertility preservation options with your doctor before starting treatment. You should not breastfeed during treatment and for at least 7 months after stopping Pertuzumab/Trastuzumab. You should not become pregnant during treatment. You should use an effective birth control method during treatment and for at least 7 months after stopping Pertuzumab/Trastuzumab. If you have a partner who could become pregnant, you should use an effective birth control method during treatment and for and for at least 7 months after stopping Pertuzumab/Trastuzumab.

Pertuzumab/Trastuzumab is used for the treatment of breast cancer.

Article last reviewed 19 August 2026
8 mins read

What is this medication for?

Pertuzumab/Trastuzumab is used for the treatment of breast cancer.

How should I take or use this medication?

Pertuzumab/Trastuzumab is usually given every three weeks as an injection into the fatty tissue under the skin.

What precautions should I take when taking or using this medication?

Inform your healthcare professional if:
- You are allergic to this medication or any of the other ingredients of this medication.
- You are taking any other medications, including supplements, traditional medications and herbal remedies.
- You have any other medical conditions.
- You are going to receive any vaccination or surgery, including dental surgery.
- You have any plans to start a family in the future.
  - Pertuzumab/Trastuzumab may have an anti-fertility effect, which could be irreversible. You should discuss fertility preservation options with your doctor before starting treatment.
You should not breastfeed during treatment and for at least 7 months after stopping Pertuzumab/Trastuzumab.
You should not become pregnant during treatment. You should use an effective birth control method during treatment and for at least 7 months after stopping Pertuzumab/Trastuzumab.
If you have a partner who could become pregnant, you should use an effective birth control method during treatment and for and for at least 7 months after stopping Pertuzumab/Trastuzumab.

What are some common side effects of this medication?

The table below will list some of the common side effects as well as the rare but serious side effects.

Side Effect	Management
Symptoms of drug allergy including one or more of the following: Swollen face/eyes/lips/tongue Difficulty in breathing Itchy skin rashes over your whole body	If you experience any of these symptoms, you should proceed to the A&E department immediately.
Mild pain, redness or swelling at the injection site	You may place a cool compress over the affected area for 15 to 20 minutes several times a day for relief. Inform your doctor if the symptoms do not go away.
Nausea or vomiting	Take small and frequent meals. Avoid foods or smells that may make you feel nauseous, such as oily, fried, or strong-smelling food. Avoid tight-fitting clothes around the waist. Your doctor may prescribe medications to help relieve or prevent nausea or vomiting. Take these as instructed.
Diarrhoea (loose and frequent stools)	Drink plenty of clear fluids (at least 2 litres or 8 glasses every day). Eat food that is gentler on the stomach such as porridge or soup. Avoid milk, dairy products, high-fibre food and oily or spicy food. Your doctor may prescribe medications to help relieve diarrhoea. Take these as instructed. Proceed to the A&E Department immediately if you have very bad diarrhoea (for example increase in bowel movement of more than 4 times per day) that does not improve even after taking medications for diarrhoea.
Muscle aches and/or joint pain	Mild pain can be relieved by taking Paracetamol. Inform your doctor if the pain does not get better. Do not take Paracetamol if you are having a fever at the same time. Taking regular warm baths may help.
Lung problems	Proceed to the A&E department immediately if you have any new or worsening symptoms of lung problems such as shortness of breath, cough, or chest pain.
Heart problems	You will require tests to check how well your heart is working before, during and sometimes after treatment. Proceed to the A&E department immediately if you have Increased shortness of breath or difficulty breathing Tightness in your chest or chest pain Unusually fast or irregular heartbeat Sudden swelling of legs

What else should I know about this medication?

Tips to help manage your condition while you are on Pertuzumab/Trastuzumab

Exercise	Light exercise is recommended as it helps to improve mobility, balance, and even emotional well-being. Avoid strenuous exercise, and rest when you are feeling tired.
Adequate hydration	Maintain adequate hydration with 2 to 3 litres of fluids per day unless you have been informed by your doctor to limit how much fluids you can drink. This will decrease your chances of getting constipation and prevent dehydration.
Medical and dental treatment	If you need to go to the hospital for any reason other than cancer, always inform the doctors and nurses that you are receiving anti-cancer treatment. Talk to your cancer doctor if you think you need dental treatment. Always inform your dentist that you are receiving anti-cancer treatment.
Seek support if you feel overwhelmed	It is normal to feel fearful or worried about your condition. Do not be afraid to talk about your concerns with your healthcare team or loved ones. There may be resources and support available to help you.

Disclaimer

Please take note that the above is not a complete list of all possible side-effects. If you have any concerns about your medication or if you have other side-effects that you think are caused by this medication, please consult your doctor or pharmacist. If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (NHG Health, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.