Other medicines and oral chemotherapy

Yes, and interactions are one of the most common and preventable problems with oral cancer treatment. Many people taking chemotherapy tablets also take medicines for blood pressure, diabetes, heart disease, acid reflux, pain, sleep, mood, infections or seizures, and they may buy others from a pharmacy without a prescription. Some of these medicines change how oral chemotherapy is absorbed, broken down by the liver or cleared by the kidneys. Others add to the same side effects, such as bleeding, heart rhythm changes or low blood counts. The result can be a treatment that works less well, or one that causes more side effects than expected.

Several groups of medicines deserve particular attention. Acid-reducing tablets and antacids can reduce absorption of some targeted cancer tablets that need stomach acid to dissolve. Some antibiotics, antifungals and medicines for tuberculosis or seizures strongly affect liver enzymes and can raise or lower chemotherapy levels. Blood thinners such as warfarin can interact with capecitabine and other medicines, increasing bleeding risk. Painkillers such as ibuprofen and diclofenac can affect kidneys and bleeding. Some heart and anti-sickness medicines affect heart rhythm. Herbal and ayurvedic products add further uncertainty. Because of this, every new medicine, including those from other doctors and over the counter, should be checked by your oncology team or pharmacist before you start it. This page describes categories only; it cannot tell you whether a particular combination is safe.

Tell every doctor you see

Dentists, family doctors and specialists all need to know you are taking oral chemotherapy.

Bring a full list

Include prescriptions, pharmacy medicines, vitamins, herbal products and eye drops.

Do not stop existing medicines

Never stop a medicine because of a possible interaction without talking to your team first.

It cannot tell you whether any particular medicine is safe with your chemotherapy. Interactions depend on the exact medicines, doses and timing, and on your kidney and liver function. Only a pharmacist or doctor with your full list can check properly.

It also cannot tell you to stop or change any medicine. Stopping blood pressure, heart, seizure or diabetes medicines suddenly can be dangerous. Any change must be planned with your doctors.

Antacids and timing

Sometimes an interaction can be managed simply by taking medicines at different times. Ask for a clear schedule.

Blood thinners need monitoring

If you take warfarin or similar medicines, extra blood tests may be needed during treatment.

Antibiotics for infections

If another doctor prescribes antibiotics or antifungals, tell them about your chemotherapy, and let your oncology team know.

Eye drops, creams and inhalers

Include these on your list. Some can still interact.

Vaccines

Some vaccines are not suitable during treatment. Check with your team first.

Older adults with many medicines

People taking many medicines benefit most from a full review, which may simplify treatment.

Pharmacy medicines for colds and pain

Cough syrups, cold remedies and painkillers can interact. Ask the pharmacist and mention your chemotherapy.

Keep your list updated

Update your medicine list whenever anything changes.

How interactions happen

Most medicines are broken down in the liver by a family of enzymes before being cleared from the body. Some medicines speed up these enzymes, so chemotherapy is broken down faster and levels in the blood fall, which can make treatment less effective. Other medicines slow the enzymes down, so chemotherapy builds up and side effects increase. Some medicines compete for the same routes out of the body through the kidneys. Others change stomach acidity or gut movement, affecting absorption. And some medicines simply add to the same effects, such as thinning the blood, lowering blood counts or affecting heart rhythm. Because these mechanisms are complex and specific to each medicine, a pharmacist with access to interaction information is the best person to check your full list.

When another doctor treats you

People on oral chemotherapy often see other doctors for infections, diabetes, heart problems, dental work or pain. These doctors may not know which cancer tablets you are taking, or may not be familiar with their interactions. Carry your safety card or a written medicine list, tell every doctor that you are on oral chemotherapy before they prescribe, and ask them to check with your oncology team if they are unsure. After any new prescription, call your oncology team or pharmacist to confirm it is safe before taking the first dose, unless it is an emergency.

Keeping one pharmacy where possible

Using the same pharmacy for all your medicines, where practical, allows the pharmacist to spot interactions across everything you take, rather than seeing only part of the picture.

Stopping other medicines safely

If your team decides another medicine should be paused or changed, they will explain how. Some medicines must be reduced gradually rather than stopped suddenly.

What to do next

Make a complete list of all medicines and supplements, ask for an oncology pharmacist review, check before starting anything new, tell every doctor and dentist about your chemotherapy, never stop other medicines without advice, and report new side effects after any change.