Trastuzumab

What is trastuzumab?

Trastuzumab is a prescription medicine used to treat certain cancers, especially HER2-positive breast and stomach cancers. It belongs to a class of treatments known as monoclonal antibodies, which are a type of targeted therapy. Brand names include Herceptin, Herzuma, Kanjinti, Ontruzant, Trazimera, and Zercepac[1].  

What is trastuzumab used for?

Trastuzumab is prescribed to treat cancers that test positive for the HER2 protein. These include[1]: 

• Early and advanced breast cancer 

• Stomach cancer (gastric cancer) 

• Gastro-oesophageal junction cancer  

How does trastuzumab work?

Trastuzumab targets the HER2 receptors found on the surface of some cancer cells. This helps by[1]: 

• Blocking signals that tell cancer cells to grow 

• Marking cancer cells for destruction by the immune system 

• Slowing or stopping the growth of HER2-positive cancer cells  

Who can take trastuzumab?

You may be prescribed trastuzumab if you are 18 or over, have HER2-positive cancer, and your heart function is healthy. You should speak to a doctor first if you[1]: 

• Have a history of heart problems 

• Are allergic to trastuzumab or its ingredients 

• Have poorly controlled high blood pressure 

• Have severe breathing problems because of cancer or you have oxygen therapy 

• Are pregnant, planning to become pregnant, or are breastfeeding 

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

What is the typical dosage of trastuzumab?

Trastuzumab dosing is based on your body weight and the specific cancer being treated. It is usually given once every 1 to 3 weeks, depending on how often you get your treatment. Treatment typically lasts up to 1 year, depending on how you respond. After your first treatment, you’ll be given a slightly lower dose, which will then stay the same for the duration of your treatment[1]. 

How do you take trastuzumab?

Trastuzumab is administered in one of two ways[1]: 

• Intravenous infusion – slowly injected into a vein in a hospital or clinic setting 

• Subcutaneous injection – injected under the skin, usually into the thigh. This may be done at home under supervision in some cases  

Can you stop taking trastuzumab?

You should not stop treatment without medical advice. Ending treatment early may reduce its effectiveness[1].  

What do you do if you take too much trastuzumab?

Overdoses are rare since it is usually administered by healthcare professionals. If you are using it at home and suspect an overdose, contact your doctor, pharmacist or go to A&E immediately[1].  

What do you do if you forget to take trastuzumab?

If you miss a scheduled dose, contact your treatment team as soon as possible. They will help you rearrange your treatment[1].  

How do you store trastuzumab?

If you are given trastuzumab to keep at home[1]: 

• Store in a refrigerator at 2°C to 8°C 

• Do not freeze 

• Keep in the original packaging away from light 

• Keep out of reach of children  

What medicines can’t you take with trastuzumab?

Some medicines may interact with trastuzumab and so should be used with caution or avoided. You should inform your doctor or pharmacist if you are taking[1]: 

• Other chemotherapy drugs 

• Heart medicines such as beta-blockers 

• Vaccines – especially live vaccines 

• Herbal supplements, including St John’s Wort  

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of trastuzumab?

Like all medicines, trastuzumab can cause side effects. Common side effects include[1]: 

• Fever and chills (especially after the first dose) 

• Nausea or vomiting 

• Diarrhoea 

• Tiredness 

• Headache 

• Skin rash 

• Muscle or joint pain 

Serious side effects include[1]: 

• Shortness of breath or chest pain 

• Swelling of the face, lips, or throat (signs of an allergic reaction) 

• New or worsening heart problems 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include[1]:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about trastuzumab

How long do I need to take trastuzumab? 
Treatment often lasts up to a year, but your doctor will decide based on your condition[1]. 

Can I take trastuzumab during pregnancy? 
It is not usually recommended during pregnancy. Always consult your specialist[1]. 

Can I store trastuzumab at home? 
Yes, but it must be kept in the fridge, in its original packaging[1]. 

Is trastuzumab chemotherapy? 
No, it’s a targeted therapy, although it’s often used alongside chemotherapy[1]. 

Will I lose my hair on trastuzumab? 
Trastuzumab alone usually does not cause hair loss, but hair loss may occur if used with chemotherapy[1]. 

For the official NHS guide to trastuzumab, visit their website.