Medical Oncologist
Gefitinib (Iressa) side effects
Gefitinib Side Effects: — The Complete List and Timeline
Gefitinib most often causes a skin rash and diarrhoea. Most side effects are manageable and appear in the first few weeks. A small number of reactions — particularly new breathlessness — are serious and need same-day action.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- Rash is the most common reaction — An acne-like rash on the face and upper body appears in most people, usually in the first few weeks.
- Most side effects appear early — The majority of reactions begin in the first month. Nail and liver changes can appear later.
- New breathlessness is a red flag — Interstitial lung disease is rare but serious. Any new cough or shortness of breath needs same-day emergency care.
- Blood tests monitor your liver — Liver enzyme changes are usually found on routine blood tests before you notice any symptoms.
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Gefitinib most commonly causes a skin rash and diarrhoea, usually appearing in the first few weeks. Most side effects are manageable, but interstitial lung disease — new breathlessness or dry cough — is a rare, serious reaction needing same-day emergency care. ESMO and NCCN guidance asks you to report any new breathing difficulty immediately.
What side effects does gefitinib cause and when do they appear?
| Side effect | Typically starts | How common | Call your team if... |
|---|---|---|---|
| Typically starts | Most reactions: first few weeks | Liver and nail changes: weeks to months | Lung reactions: any time — act immediately |
| Skin rash or acne-like spots | First few weeks | Very common | Rash spreads to chest or back, weeps, crusts, or looks infected |
| Diarrhoea | First few weeks | Very common | Clearly worse than usual for over 24 hours, or with blood, fever, or pain |
| Nausea or loss of appetite | First few weeks | Common | Cannot eat anything for over 24 hours, or with persistent vomiting |
| Dry skin and cracked fingertips | Weeks into treatment | Common | Skin is bleeding, infected, or a break is not healing |
| Nail changes or paronychia | Weeks to months in | Common | Nail is lifting, very painful, or shows pus or signs of infection |
| Mouth sores | First few weeks | Common | Cannot eat or drink, or sores are spreading rapidly |
| Eye redness or irritation | First few weeks | Common | Eye pain, change in vision, or significant sensitivity to light |
| Raised liver enzymes | Any time — found on blood tests | Common | Yellowing of skin or eyes, dark urine, or pain under the right rib |
| New cough or breathlessness | Any time | Uncommon — but serious | Any new or worsening breathlessness or dry cough — go to hospital the same day |
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Why does gefitinib cause a skin rash, and what should you do about it?
Gefitinib blocks the EGFR protein, which cancer cells use to grow. That same protein is active in the skin and its oil glands, so blocking it causes an acne-like rash on the face, scalp, and upper body in many people.
The rash is not an allergy. It does not mean the drug is harming you.
Tell your oncology team at your next appointment even if the rash feels mild. They will grade it and advise on treatment. If the rash becomes very widespread, painful, or infected before your appointment, call the same day.
What should I know about each specific gefitinib side effect?
How long does the diarrhoea last?
Diarrhoea from gefitinib often appears in the first few weeks. It can settle with time, though it varies considerably between people — some have it intermittently throughout treatment. Do not take loperamide or similar medicines without asking your team first, because they can mask a worsening that needs medical attention. Any diarrhoea that is clearly increasing day on day, or that comes with blood, fever, or abdominal pain, needs a call the same day.
Is the rash permanent?
No. The rash usually improves with treatment — prescription creams or antibiotics your oncologist recommends — and resolves after gefitinib is stopped. During treatment it may fluctuate rather than clearing completely. Mild rash on the face and upper chest rarely needs changes to your treatment plan. Widespread, painful, or infected rash may mean a dose pause. Tell your team about the rash at every visit, even when it feels minor, so they have a baseline to compare against.
What are the nail changes and can they be prevented?
Nail changes — known as paronychia — are partly preventable. Keeping nails trimmed short, wearing gloves for wet work, and avoiding trauma to the nail edges can reduce the risk. The condition involves inflammation and sometimes infection around the nail edges. It appears later than most gefitinib side effects, typically weeks to months into treatment. Once paronychia develops, your team will advise on antiseptic soaks, topical creams, or oral antibiotics if the nail bed is infected. Let your team know at your next appointment, or sooner if the area is very painful or showing pus.
What is interstitial lung disease and how serious is it?
Interstitial lung disease — sometimes called pneumonitis — is inflammation of the lung tissue. It is uncommon with gefitinib, but it can be life-threatening if not caught early. The warning signs are a new dry cough, breathlessness that was not there before, or fever. Any one of those appearing during treatment means go to hospital the same day — do not wait to see if it settles. It can appear at any point in treatment, which is why your team treats any new respiratory symptom as urgent regardless of when it occurs.
Will my liver tests always show something abnormal?
Raised liver enzymes are fairly common on gefitinib and are usually found on routine blood tests before you feel anything. Mild elevation often settles without any change to treatment. More significant elevation may need a dose pause. This is why your team schedules regular blood monitoring — to catch changes before they become symptomatic. The signs that mean you should not wait for your next test are yellowing of the skin or the whites of the eyes, unusually dark urine, or pain under the right rib cage. If you notice any of those, go to hospital the same day.
Did you know?
Gefitinib only works where the tumour carries a specific EGFR mutation. ESMO guidelines require that mutation testing be completed before the drug is prescribed.
Every person taking gefitinib has already had their tumour's molecular biology confirmed. This is why its side effect profile looks so different from chemotherapy — it targets one pathway, not all rapidly dividing cells.
Source: ESMO Clinical Practice Guidelines: Metastatic Non-Small-Cell Lung Cancer
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- Osimertinib vs Gefitinib and Erlotinib: Is the Costlier Drug Worth It?
- Rash, Dry Skin and Nail Problems on Osimertinib
- Taking Osimertinib: Food, Timing and What to Do If You Miss a Dose
- Tests and Monitoring While You Are on Osimertinib
- When Osimertinib Stops Working: Resistance and What Comes Next
- Who Is Eligible for Osimertinib? EGFR-Mutant Lung Cancer
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Common questions
Frequently asked questions
Is the skin rash from gefitinib dangerous?
The rash is not dangerous in itself and is not an allergic reaction. It appears because gefitinib blocks EGFR, which is active in skin cells as well as in the tumour. Most rashes are mild and can be managed with moisturisers, gentle cleansers, and prescription creams when needed. The rash becomes a reason to call your team if it spreads widely to the chest and back, weeps or crusts over, or shows signs of infection — pain, warmth, or pus. Blistering or peeling skin is rare but needs emergency review.
Can I take over-the-counter medicines for gefitinib side effects?
Ask your oncology team before taking anything bought from a pharmacy, including anti-diarrhoeals, skin creams with active ingredients, and pain relievers. Some interact with gefitinib or can mask worsening symptoms that your team needs to assess. Your team can prescribe treatments that address the cause rather than just the symptom, so it is worth calling before reaching for a pharmacy shelf option.
Do side effects mean gefitinib is not working?
Side effects and treatment effectiveness are separate things. Having more side effects does not mean the drug is working better, and having fewer does not mean it is failing. Response is assessed through scans and blood tests, not through how you feel day to day. If you are concerned about whether the treatment is controlling your cancer, that is a question for your oncologist at your next review — not something the side effect picture can answer.
Should I avoid any foods or medicines while taking gefitinib?
Yes. Gefitinib is broken down by liver enzymes that interact with several common drugs and foods. Certain epilepsy medicines, tuberculosis treatments, some antifungals, some antibiotics, and St John's Wort can all change how much gefitinib is active in your body. Grapefruit and grapefruit juice can also interact. Give your oncology team and your pharmacist a complete list of everything you take — including herbal remedies and Ayurvedic medicines — before you start.
What happens if a side effect is severe enough to stop treatment?
Gefitinib can be paused and restarted at the same or a reduced dose, depending on how severe the reaction was and how well it responds to treatment. The decision weighs the benefit the drug is providing against the harm the side effect is causing. Stopping permanently is not always the outcome — many people restart successfully after a pause. If you are struggling with a side effect that feels unmanageable, call your team rather than stopping on your own, so they can help you through it while protecting your treatment.