FOLFIRI — What This Regimen Is and What to Expect

Each part of the acronym names one of the three drugs: FOL stands for folinic acid, F for fluorouracil and IRI for irinotecan. Knowing this matters because it tells you which drug is responsible for which side effects. Irinotecan — the IRI — is the drug most people notice first, through diarrhoea and, for many, temporary hair thinning. The other two drugs are shared with several related regimens.

FOLFIRI is given in repeated cycles, with a rest period between each to allow your body to recover. The number of cycles planned is decided individually and will be discussed with you before treatment starts. Your oncologist will explain the schedule for your specific case and when blood tests are scheduled to monitor how your body is responding.

Hair thinning or loss is common with FOLFIRI because of irinotecan. The extent varies between individuals — some experience significant loss, others notice thinning. It is usually temporary and hair typically grows back after treatment ends. It does not fall out all at once; if it happens, it usually begins some weeks into treatment. Ask your team whether a cold cap is appropriate for your situation.

Contact your oncology team the same day — not at your next scheduled appointment. Severe diarrhoea can cause dehydration very quickly. If you cannot keep fluids down, or if there is blood in the stool, go to the emergency department rather than waiting for a callback. Your team will have given you guidance before treatment started about when to call; follow that guidance and err on the side of calling earlier rather than later.

Many people find appetite and food tolerance change during FOLFIRI cycles. Nausea, mouth sores and taste changes can all affect what you want to eat. Small, frequent meals often suit better than larger ones. If diarrhoea is active, your team will advise which foods to avoid temporarily. Do not restrict eating severely without guidance — the body needs nutrition to recover between cycles. Tell your team if eating has become very difficult.

They are not directly comparable in the way that question implies. Both regimens share two of their three drugs and are used for some of the same cancers, but the choice between them is about matching the side-effect profile to your individual situation, health and preferences — not selecting the stronger one. FOLFOX neuropathy can persist after treatment ends, sometimes permanently, whereas FOLFIRI diarrhoea does not follow that long-term pattern. Your oncologist will explain why one was recommended for you specifically.