Irinotecan

What this treatment is and how it works

It blocks topoisomerase I, an enzyme that helps cells handle DNA (the genetic instructions inside cells) during division. It is different from liposomal irinotecan.

When it may be used

Your team may use this treatment in the following settings: Colorectal and pancreatic cancers and selected other cancers. The choice depends on the exact diagnosis, stage, previous treatment, health and treatment aim. Treatment may aim to cure cancer, lower the risk of recurrence, or control cancer and symptoms, depending on the setting.

A listed use is not a claim that every brand is licensed for that use in every country. Your oncologist will explain why this treatment is appropriate for you.

Before treatment

Before starting, tell the team about previous cancer treatment, allergies, infection symptoms, heart, lung, kidney or liver disease, hearing or nerve problems, diabetes and all medicines you take. Discuss pregnancy, contraception and fertility. Ask for a written treatment calendar, supportive-medicine instructions and a 24-hour oncology contact number. Baseline blood tests usually include a full blood count and kidney and liver function; additional tests depend on the medicine and your health. Before chemotherapy that reaches the whole body, the team should check for current or past hepatitis B infection. If a test is positive, extra monitoring or antiviral treatment may be needed to prevent the virus becoming active again. The team will coordinate testing and treatment; do not delay urgent cancer treatment yourself.

How treatment is given and the schedule

An infusion into a vein, usually as part of a combination. The nurse watches for early sweating, cramping, a runny nose or sudden diarrhoea.

Often every 2 weeks in FOLFIRI (fluorouracil, folinic acid and irinotecan) or FOLFIRINOX (the same medicines plus oxaliplatin), but other schedules are used. The prescribed regimen determines the infusion and dose.

The dose is calculated for your treatment and health. Rest periods, delays or dose changes may be needed. Do not change doses or treatment dates yourself, except to follow specific instructions to stop a medicine and seek help for warning symptoms. The team will give you a revised plan when needed.

During an infusion, tell the nurse immediately about pain, burning, swelling or leaking around the cannula or line. Do not massage the area or apply heat or ice unless the team instructs you.

Tests and monitoring during treatment

Blood counts, liver function, hydration and bowel symptoms are checked. Reduced activity of UGT1A1, an enzyme that helps clear the active form of irinotecan, can increase the risk of severe diarrhoea and low white cells; the team may recommend testing or a dose adjustment in selected patients.

At each review, describe symptoms since the previous dose, including problems that have already settled. Blood tests can detect effects before you feel them. Your team may delay, reduce, omit or stop a medicine if results or symptoms make this necessary. The decision depends on the exact protocol; a normal result does not make new symptoms safe to ignore.

Side effects: what to expect

Frequency varies with the dose, schedule, cancer and other treatments. “Common or more frequent” is a practical grouping, not a single percentage for every patient. Some serious effects appear in more than one group because severity and frequency are different.

You are unlikely to have all of these effects. This is not an exhaustive list. Tell the team about any new or troublesome symptom, including one not mentioned here.

Common or more frequent side effects

Other reported side effects (frequency varies)

These effects may be common in some treatment settings, less common in others, or have no reliable frequency estimate. Their position here does not mean they are necessarily less frequent or less serious.

Constipation, dehydration, abdominal discomfort and liver-test abnormalities can occur. Symptoms during or shortly after an infusion may reflect an early cholinergic reaction.

Report these at review, or sooner if worsening. Use the urgent guidance for symptoms that affect breathing, drinking, urination, walking, consciousness or bleeding.

Important serious side effects, including rare effects

Serious does not always mean rare. Where reliable incidence is unavailable, no numerical frequency is assigned. The action to take matters even when the likelihood is uncertain.

Severe delayed diarrhoea

Irinotecan-related diarrhoea can cause dehydration and infection. Start the written treatment plan promptly and contact the oncology team. Fever, blood, severe cramps, dizziness, reduced urine or inability to drink requires urgent assessment.

Severe bowel inflammation or damage

Severe abdominal pain, a swollen abdomen, bloody diarrhoea, persistent vomiting or fever with bowel symptoms needs urgent assessment. Do not treat these symptoms simply by taking extra antidiarrhoeal medicine or laxatives.

Inflammation or injury in the lungs

A new cough, breathlessness, chest discomfort or falling exercise tolerance needs urgent oncology contact. Severe or rapidly worsening breathing difficulty is an emergency. Infection and other causes must also be considered.

Severe infusion or allergic reaction

Itching, flushing, wheeze, dizziness, throat tightness or facial swelling can start during an infusion or later. Tell the nurse immediately. Severe breathing difficulty, collapse or sudden face/throat swelling is an emergency.

Practical advice for this treatment

Obtain the irinotecan-specific diarrhoea plan before going home. Early cramping and sweating during or within about 24 hours of treatment can be treated by the team, often with atropine. Delayed diarrhoea starts later and needs the prescribed antidiarrhoeal plan plus prompt contact. Do not use an over-the-counter dosing schedule as a substitute.

Medicines, interactions and vaccinations

Give the oncology pharmacist a complete list of prescription medicines, over-the-counter products, vitamins, herbal and Ayurvedic remedies and supplements. Ask before starting anything new. Do not stop prescribed medicines, including anticoagulants or infection-prevention medicines, without a coordinated plan. Live vaccines are generally unsuitable while immunity is suppressed; discuss vaccine type and timing with the team. Non-live vaccines may be offered, although protection can be reduced. Follow any specific stop-and-call instructions for the cancer medicine on this page or in your written treatment plan.

Strong enzyme inhibitors or inducers, including some antifungals, antibiotics, anticonvulsants and St John’s wort, can change exposure. Review laxatives and diarrhoea medicines with the team.

Pregnancy, fertility and breastfeeding

Chemotherapy can harm a developing baby and may affect fertility temporarily or permanently. Discuss sperm, egg or embryo storage before treatment when feasible. If you could become pregnant, or your partner could become pregnant, use effective contraception during treatment and for the drug-specific period afterwards. Ask for a written end date based on every medicine in your plan: the required period differs by product and can extend for months. Periods stopping does not guarantee infertility. Tell the team immediately about a suspected pregnancy. Do not breastfeed during treatment; restart only after the team confirms the interval for the exact medicine and formulation.

Everyday life

Gentle activity, regular meals and rest can help you cope. Prepare food hygienically and drink according to your individual fluid plan. Avoid smoking; ask whether alcohol is safe with your exact treatment and other medicines. Plan work, travel and driving around symptoms and monitoring visits. Do not drive if dizzy, sleepy, weak, visually affected or impaired by neuropathy. You can usually be close to family and friends: chemotherapy does not make you radioactive. Follow the unit’s instructions for handling urine, vomit, laundry and sexual precautions for the period it specifies.

When to contact the oncology team

Contact the oncology team the same day for persistent vomiting or diarrhoea, difficulty drinking, reduced urine, mouth pain affecting eating, new cough, jaundice, a painful or spreading rash, unusual bruising, worsening constipation or new nerve symptoms. Use the more urgent instructions for the particular symptom when given above. If the team cannot be reached and you are unwell, seek urgent medical care.

Write down your hospital’s daytime and out-of-hours numbers before treatment. CTI’s general contact details do not replace the emergency number provided by your treating hospital.

After treatment

Keep the planned blood tests and follow-up appointments after the last dose. Blood counts and immunity may take time to recover, and some effects can start or persist later. Contact the team about symptoms rather than waiting for a routine visit. Keep a treatment summary, including drug names, dates and any serious reactions, for future doctors. Response may be assessed with examination, scans or blood or marrow tests, depending on the cancer.

Words you may hear

UGT1A1

An enzyme involved in clearing the active form of irinotecan. Inherited differences can affect toxicity.

Frequently asked questions

Related combination guides

• FOLFIRI
• FOLFOXIRI
• FOLFIRINOX / modified FOLFIRINOX