Medical Oncologist
Targeted therapy
Osimertinib (Tagrisso): — The Complete Patient Guide
Osimertinib is a once-daily tablet prescribed for lung cancer that carries a specific EGFR gene mutation. It targets that mutation directly, works differently from chemotherapy, and is taken at home. If you have just been prescribed it, this page explains what it is, why you are eligible, and what to expect.
Medically reviewed by Dr. T. Raghavender Reddy, Medical Oncologist, MBBS · DM (Medical Oncology) · MD (Radiation Oncology) · Last reviewed August 2026
- A tablet, not an infusion — You take osimertinib once a day at home, not in a day-care chair.
- For EGFR-mutated lung cancer only — Your gene test result is what makes you eligible — not the cancer type or stage alone.
- Targeted, not chemotherapy — It acts on a specific fault in your cancer cells, which changes the side-effect profile.
- Reaches the brain — It crosses into brain tissue more reliably than older EGFR drugs, which matters if brain metastases are or were a concern.
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Osimertinib, sold as Tagrisso, is a once-daily tablet for non-small cell lung cancer that carries a specific EGFR mutation. It targets the mutation directly, leaving most normal cells alone. NCCN and ESMO list it as a preferred first-line option for eligible patients. You take it at home, not by infusion.
What is osimertinib and who is it prescribed for?
Osimertinib is a targeted therapy for non-small cell lung cancer that carries a change in the EGFR gene. You take one tablet a day at home, at the same time each day.
Before prescribing it, your oncologist will have tested your tumour tissue for EGFR mutations — specifically the exon 19 deletion or the exon 21 L858R change. If neither is present, osimertinib does not work. The test result is what makes you eligible, not the cancer type alone.
It is also used when lung cancer has returned after an earlier EGFR-targeting drug and a new change called T790M is found on re-testing. In that situation, NCCN, ASCO and ESMO all list osimertinib as the recommended option.
What should you know before taking your first dose?
- Take it at the same time each day — morning or evening, whichever you will remember.
- You can take it with or without food.
- Swallow the tablet whole. Do not crush or chew it.
- Tell your team about every other medicine you take — including ayurvedic, herbal, and over-the-counter preparations. Some interact with osimertinib.
- Tell your team if you are pregnant, trying to conceive, or breastfeeding before you start.
- Keep all follow-up appointments. Blood tests and scans are how your team checks the drug is working and catches side effects early.
- If you miss a dose and your next one is less than 12 hours away, skip the missed dose and carry on as normal. Do not double up.
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How does osimertinib work?
Your cancer cells carry a fault in the EGFR gene that keeps sending a grow signal even when the body does not need more cells. Osimertinib attaches to the faulty protein this gene makes and blocks that signal.
Because it targets a specific fault rather than any fast-dividing cell, the side-effect profile is different from chemotherapy. Hair loss is not typical. Severe nausea is uncommon.
Osimertinib also crosses into the fluid and tissue around the brain more reliably than older EGFR-targeted drugs. This is one reason it is often preferred when brain metastases are present or have previously been treated.
What side effects should you expect?
The most common side effects are a skin rash — often on the face, scalp and chest — dry or cracked skin, changes to your nails, loose motions, and mouth sores. These are usually manageable and tend to be milder than chemotherapy side effects.
Inflammation of the lungs, called interstitial lung disease, can occur. It is uncommon but serious. New breathlessness, a cough that is new or getting worse, or fever during treatment means calling your team the same day — not waiting for your next appointment.
Osimertinib can also affect the heart's electrical rhythm. Your team will check an ECG before you start and at intervals during treatment. Tell them if you notice palpitations, feel faint, or feel your heart racing.
Did you know?
Osimertinib was developed specifically to overcome a resistance change — called T790M — that develops in many patients after first-generation EGFR drugs stop working.
NCCN and ESMO subsequently moved it to first-line use because it also controls the original mutation more effectively and reaches the brain more reliably than earlier options.
Source: NCCN Clinical Practice Guidelines in Oncology: Non-Small Cell Lung Cancer
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Drug Deep Dive: Alectinib (Alecensa)
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- Gefitinib (Iressa, Geftinat, Geftib): The Complete Patient Guide
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- Gefitinib Side Effects: The Complete List and Timeline
- Gefitinib Success Rate and Survival: An Honest Look at the Numbers
- Gefitinib and Antacids: The Interaction That Silently Reduces Absorption
- Gefitinib in Early-Stage vs Advanced Lung Cancer: Different Goals
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- Raised Liver Enzymes on Gefitinib: What Your LFT Report Means
- T790M Testing After Gefitinib Stops Working: The Next Step Explained
- Taking Gefitinib: Food, Timing and What to Do If You Miss a Dose
- Tests and Monitoring While You Are on Gefitinib
- When Gefitinib Stops Working: Resistance and What Comes Next
- Who Is Eligible for Gefitinib? EGFR-Mutant Lung Cancer
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Common questions
Frequently asked questions
Why did I need a gene test before being prescribed osimertinib?
Osimertinib only works when your cancer carries a specific EGFR mutation. The gene test — done on your biopsy tissue — is what establishes whether the drug is likely to help you. Without the right mutation present, the drug does not have a target and will not work. This is standard practice recommended by NCCN, ASCO and ESMO: the test result is the basis for the prescription, not a formality before it.
Is osimertinib a form of chemotherapy?
No. Osimertinib is a targeted therapy. Chemotherapy affects all fast-dividing cells in the body, which is why it causes hair loss and severe nausea. Osimertinib acts on a specific fault in the EGFR gene that is driving your cancer, leaving most normal cells alone. The side-effect profile is different — hair loss is not typical and severe nausea is uncommon. It has its own side effects, particularly on the skin and occasionally on the lungs, that your team will monitor for.
What happens if osimertinib stops working?
Over time, some cancers find a way around any targeted drug. If scans show the cancer is growing again, your oncologist will usually arrange a repeat biopsy or a liquid biopsy to look for new genetic changes. The result guides the next step — which may be a different targeted drug, chemotherapy, or a clinical trial. Finding the right next step depends on understanding why the first drug stopped working, which is why re-testing matters more than simply switching.
How long will I need to take osimertinib?
For most patients on it for advanced disease, there is no fixed duration. You continue for as long as the drug is controlling the cancer and the side effects are manageable. For patients taking it after surgery to reduce the risk of recurrence, NCCN guidance recommends a defined course. Your oncologist will tell you which situation applies to you and how scans and reviews will be used to track your response.
Can I take ayurvedic or herbal medicines alongside osimertinib?
Tell your team about everything you are taking before you add anything new. Some herbal preparations can change how osimertinib is processed in the body, affecting how much of the drug reaches the cancer. This is a real interaction risk, not a judgement about traditional medicine. Your oncologist can only manage it if they know what you are taking. Never stop or adjust osimertinib to accommodate a supplement — contact your team first and let them advise.
Will osimertinib affect fertility or pregnancy?
Yes. Osimertinib can harm a developing baby. Both men and women taking it are advised to use effective contraception during treatment and for a period after stopping — your team will tell you how long applies to your situation. If you are pregnant, planning a pregnancy, or breastfeeding, tell your oncologist before you start. This is a conversation that needs to happen before the first dose, not after.