Medicines, foods and supplements to avoid on trastuzumab emtansine

Trastuzumab emtansine, also called T-DM1 or Kadcyla, is a HER2 antibody joined to a chemotherapy medicine called DM1. It does not have a long list of food rules, but a few groups of medicines and remedies need care. The first group is medicines that slow down the liver enzyme that breaks down DM1. These include certain antifungal medicines such as itraconazole, ketoconazole, voriconazole and posaconazole, the antibiotic clarithromycin, and some HIV medicines such as ritonavir. Taken together, they could raise DM1 levels and make side effects worse, so the product information advises avoiding them where possible. Grapefruit and grapefruit juice act on the same enzyme, so many teams suggest avoiding them too. The second group is anything that increases bleeding, because T-DM1 often lowers platelets. Blood thinners, aspirin, clopidogrel and anti-inflammatory painkillers such as ibuprofen need a discussion before you take them. The third group is anything that strains the liver, including alcohol, high doses of paracetamol and some herbal or traditional remedies, since T-DM1 can raise liver enzymes. Hormone tablets and radiotherapy are often given alongside T-DM1 and are generally fine when your team has planned them. The simple rule is to tell your oncology team about every medicine, supplement and remedy you use, and to check before starting anything new.

Check antifungals and antibiotics

Some common prescriptions from other doctors can raise DM1 levels in your body.

Think about bleeding

Low platelets are common on T-DM1, so blood thinners and some painkillers need care.

Protect your liver

Limit alcohol and avoid unknown herbal products while your liver tests are being watched.

Interaction advice is built from laboratory knowledge, product information and experience. It is useful, but it has gaps you should know about.

No list is complete

New medicines appear all the time, and many combinations have never been formally tested with T-DM1.

Sometimes the benefit outweighs the risk

A serious fungal infection or a blood clot may need treatment that would otherwise be avoided. Your team can weigh this and monitor you more closely.

Natural does not mean safe

Herbal and traditional products can contain strong ingredients, and their contents are not always what the label says.

What this page cannot tell you

It cannot check your own list of medicines. Only your oncologist or pharmacist, looking at everything you take, can do that.

Routine health care continues during treatment, but a little planning helps it fit around T-DM1.

Vaccines

Inactivated vaccines, such as the yearly flu injection, are usually encouraged. Live vaccines need a specific discussion first. Ask your team about timing in your treatment cycle.

Dental treatment

Tell your dentist you are on T-DM1. Extractions and deep cleaning may cause more bleeding if your platelets are low, so a blood test beforehand is sensible.

Other procedures

Before any surgery, biopsy or injection, the doctor doing it should know about T-DM1 and see your recent platelet count.