Osimertinib (Tagrisso)

Osimertinib at a glance

Osimertinib is a targeted cancer medicine, also called Tagrisso. It comes as 40 mg and 80 mg tablets. The usual adult dose is 80 mg once daily, with or without food. Your prescribed dose may be different because of side effects or another medicine.

Treatment is selected using the cancer’s EGFR gene test. Osimertinib may be prescribed alone or alongside chemotherapy. Your team should explain the purpose, likely benefits, planned duration and alternatives in your situation. This page explains the medicine and its precautions; it does not replace your personal treatment plan.

Most treatment is taken at home, but regular appointments and blood tests remain essential. Diarrhoea, skin and nail changes, mouth soreness and tiredness are familiar problems. Complications involving the lungs, heart, bone marrow, eyes or muscles need prompt assessment. Reporting symptoms early helps the team support you safely.

What osimertinib does

EGFR is a protein involved in messages that tell cells to grow. Certain changes, called mutations, in the EGFR gene can leave this growth signal overactive. Osimertinib blocks the enzyme activity of some altered forms of EGFR. It belongs to the tyrosine kinase inhibitor family.

The aim may be to reduce the chance of cancer returning, or to control cancer that is present. Treatment cannot guarantee a particular result. Cancer cells can sometimes develop changes that make treatment less effective, so the team checks benefit over time. Do not judge effectiveness by the presence or absence of a rash.

Although treatment is targeted, healthy tissues can also be affected. The skin and bowel problems associated with EGFR medicines are examples. Taking a tablet does not mean that treatment is too mild to need monitoring.

How the team decides whether it is suitable

The exact EGFR result matters. Reports may mention an exon 19 deletion, L858R or T790M. These terms describe different genetic changes; they are not interchangeable. Ask which finding supports your treatment and whether any further testing is needed. A general statement that a tumour contains EGFR protein is not the same as a suitable mutation result.

Testing may use a tumour sample or, in appropriate circumstances, tumour DNA circulating in blood. A negative blood result can miss a mutation. The team may therefore recommend tissue testing where possible. The appropriate sample depends on your clinical situation.

Previous treatment, chest radiotherapy, heart and lung health, other medicines and your priorities all influence the decision. Evidence for children is not established in the prescribing information. European information does not recommend treatment in severe liver disease. End-stage kidney failure or dialysis need specialist consideration because evidence is limited. Tell the team about any allergy to osimertinib or its ingredients; European information lists this as a reason not to take it.

Before treatment starts

Bring a complete medicine list, including non-prescription tablets, herbal products and supplements. Tell the team about previous lung inflammation, chest radiotherapy, fainting or an abnormal heartbeat, heart failure, eye problems, hepatitis B, unexplained bleeding and muscle disease. Mention pregnancy, breastfeeding or plans for a family.

A full blood count checks infection-fighting cells, red cells and platelets. Kidney and liver tests help establish a baseline. An ECG records the heart’s electrical rhythm; an echocardiogram or similar test assesses pumping strength when required. These answer different questions. Pregnancy testing is needed when pregnancy is possible.

Ask for a written dosing and missed-dose plan, the dates of your next tests, and a 24-hour contact number. If chemotherapy accompanies osimertinib, obtain its separate instructions, including supportive medicines and appointment dates. Do not assume the tablet replaces those precautions.

Tell the team if you have ever had hepatitis B, even if you feel well now. European information warns that previous infection can reactivate. People with positive hepatitis B tests need clinical and laboratory monitoring. Reactivation requires a treatment pause and specialist management.

How to take osimertinib

Take your prescribed dose at approximately the same time each day. Food is optional. Swallow the tablet whole with water; do not split, crush or chew it. Do not change between 80 mg and 40 mg yourself. If you accidentally take too much, contact the team or an emergency department immediately.

Missed-dose instructions differ. US prescribing information says to skip the missed dose and take the next scheduled dose. European information allows a forgotten dose unless the next dose is due within 12 hours. Obtain the instruction for your supplied product in writing; if uncertain, check before taking a late dose. Never take two doses together. If you vomit after taking a tablet, do not take an extra tablet; take the next dose at its usual time unless your team advises otherwise.

A tablet can be dispersed in water if swallowing is difficult, but it must not be crushed. Use only still, non-fizzy water. Stir until small pieces form; the tablet will not completely dissolve. Drink immediately. The water and rinse volumes differ between product instructions:

• US instructions use 60 mL of water, followed by a container rinse with 120–240 mL of water, which you drink immediately.
• The European patient leaflet uses 50 mL of water, followed by a further 50 mL rinse, which you also drink. Its professional information describes the rinse as half a glass.

Ask your pharmacist to demonstrate the instructions for your pack. Do not use juice, milk or hot water, or heat the mixture. If you have a fluid restriction, discuss these volumes; do not simply omit the rinse and leave medicine behind.

Nasogastric tube administration is described in both labels, using 15 mL for initial dispersion and 15 mL for residue rinsing, followed by appropriate tube flushes. All dispersion and residues must be administered within 30 minutes of adding water. This needs a pharmacist-approved plan for the tube; it is not permission to use any feeding tube or improvise a preparation.

Keep tablets in their original packaging, away from children and pets. US storage instructions specify 20–25°C (68–77°F); European information has no special storage requirement. Follow your pack and avoid excessive heat and damp. Return unused tablets to a pharmacy. Do not share them or put them into household wastewater.

Monitoring and checking benefit

Your team reviews symptoms, blood results and scans appropriate to your treatment goal. A full blood count is checked before treatment and periodically thereafter, with additional checks if symptoms suggest a problem. Kidney and liver results may also need monitoring. Keep a brief record of doses, bowel changes, rashes, breathing symptoms and new medicines.

ECGs and blood salts, such as potassium and magnesium, require particular attention if you have heart disease, a tendency to a prolonged QT interval, or medicines affecting heart rhythm. Heart pumping tests are especially relevant with cardiac risk factors or new symptoms. US instructions require pumping-function assessment before and during osimertinib with pemetrexed and platinum chemotherapy in all patients; monotherapy assessment is directed particularly to those with cardiac risk factors.

The September 2026 US update recommends periodic testing of creatine phosphokinase, or CPK, during treatment and additional testing for unexplained muscle pain or tenderness. CPK is a muscle enzyme. European information also warns about muscle inflammation and breakdown, with assessment when symptoms occur. Ask how muscle monitoring fits into your blood-test plan.

There is no single scan or blood-test timetable suitable for everyone. A dose pause or reduction may allow a problem to settle. Some confirmed serious reactions require permanent stopping. Never restart after a medically advised pause without instructions.

Common side effects and practical care

Blood counts can fall: low white cells increase infection risk, low platelets cause bruising or bleeding, and low red cells cause anaemia. Report infection symptoms, unexplained bleeding or marked breathlessness promptly. These changes are distinct from rare aplastic anaemia.

Loose stools can begin during treatment. Note how often you go compared with your normal pattern, and use prescribed anti-diarrhoea medicine as directed. Take frequent drinks within any fluid restriction. Seek advice promptly if diarrhoea persists, worsens, prevents drinking, occurs with fever or abdominal pain, or leaves you dizzy or passing little urine. Do not keep increasing over-the-counter treatment without advice.

Dry skin and an acne-like rash are common. Use gentle washing products and a plain moisturiser. Report soreness, itching or a rash early so the team can offer treatment. Avoid harsh acne preparations unless recommended. A painful spreading rash, blisters or sores involving the eyes or mouth requires urgent assessment rather than routine skin care.

Nails may become brittle, ridged or discoloured. The skin around them can become inflamed or infected. Protect hands during wet work, wear comfortable footwear and avoid picking at cuticles. Tell the team about redness, swelling, pus or pain around a nail; treatment may prevent a small problem becoming more difficult.

For mouth soreness, use gentle oral care with a soft toothbrush. Ask for a recommended mouthwash or pain relief. Avoid foods that sting. Contact the team if swallowing is difficult, you cannot drink adequately, or there are white patches or extensive ulcers.

Tiredness may reflect treatment, poor sleep, reduced eating or anaemia. Balance rest with gentle activity that feels manageable. Tell the team about a marked change rather than assuming fatigue is inevitable. Smaller meals and dietitian support can help with reduced appetite. Hair can thin, although the pattern also depends on accompanying treatment.

Important serious side effects

Lung inflammation, also called interstitial lung disease or pneumonitis, can be life-threatening. New or worsening breathlessness, cough or fever needs immediate assessment. Infection, cancer and effects of radiotherapy can produce similar symptoms, so the cause cannot be decided at home. Treatment should be withheld while suspected drug-related lung inflammation is investigated; contact the team immediately before another dose.

Management after definitive chest chemoradiotherapy needs special care. US instructions allow continued treatment or a pause for grade 1 inflammation, but require permanent stopping for grade 2 or worse; without recent definitive chemoradiotherapy, confirmed drug-related ILD/pneumonitis requires permanent stopping. European instructions distinguish drug-related ILD from radiation pneumonitis: some grade 2 radiation pneumonitis can be treated with a pause and later restart, but symptoms lasting more than 4 weeks or recurrent grade 2 radiation pneumonitis require permanent stopping. These grades are clinical assessments, not a home checklist. Your specialists must decide the cause and applicable restart rules.

Osimertinib can alter the QT interval, part of the heart’s electrical cycle, and can weaken heart pumping. Palpitations, fainting, new breathlessness, swollen ankles or rapid unexplained weight gain need prompt attention. Severe chest pain, collapse or severe breathlessness is an emergency. An abnormal test may require a pause or dose change even before symptoms develop.

Rarely, the bone marrow can stop producing enough blood cells, called aplastic anaemia. Warning signs include fever or repeated infections, unusual bruising or bleeding, pallor and profound tiredness. This is more serious than a routine mild reduction in counts. Suspected cases need treatment interruption, urgent blood tests and specialist assessment; confirmed aplastic anaemia requires stopping osimertinib.

Severe skin reactions include Stevens–Johnson syndrome and toxic epidermal necrolysis. Painful skin, spreading blisters, peeling, target-like patches or sores affecting the mouth, eyes or genitals are urgent warning signs. Another possible reaction is inflammation of small blood vessels in the skin, causing purple spots, bruiselike areas or ulcers. Report these promptly, particularly with abdominal pain or blood in urine. Suspected severe skin reactions or vasculitis require a treatment pause and urgent assessment; confirmed severe skin reactions require permanent stopping under US guidance.

Keratitis is inflammation of the eye’s clear front surface. Eye pain, redness, light sensitivity, watering or blurred vision needs prompt eye assessment. Do not treat a painful red eye as simple dryness without advice.

Muscle inflammation and serious muscle breakdown have been reported. Report unexplained muscle pain, tenderness, weakness or difficulty moving. Dark urine or reduced urine with muscle symptoms needs urgent assessment because kidney injury can occur. Muscle problems may develop after a long time on treatment as well as earlier.

Other medicines, supplements and vaccinations

Some medicines speed up the breakdown of osimertinib and reduce its effect. Examples include rifampicin and certain epilepsy medicines such as carbamazepine and phenytoin. Do not take St John’s wort with osimertinib. Never stop an essential medicine yourself: ask the oncology pharmacist to arrange a safe alternative or plan.

US instructions contain a specialist dose adjustment if a strong enzyme-inducing medicine cannot be avoided. This is not permission to double your tablets. European advice emphasises avoiding strong inducers and caution with moderate inducers.

Other medicines may increase heart-rhythm risk or have their own levels altered by osimertinib. The pharmacist should check medicines such as digoxin, rosuvastatin and certain anticoagulants, as well as anti-sickness tablets, antibiotics and antidepressants. Do not assume all medicines in a category have the same interaction.

Omeprazole did not meaningfully change osimertinib exposure in the product-information study; routine acid-suppressant spacing is not required in the way it is for some other EGFR medicines. Nevertheless, report all stomach medicines, particularly when chemotherapy accompanies treatment. Ask before starting supplements or herbal remedies.

Discuss vaccinations with the team. Whether a live vaccine is appropriate depends on immune function, accompanying treatment and timing. There is no reason to apply another medicine’s vaccination schedule automatically to osimertinib.

Everyday life during treatment

Choose a dosing time that fits your routine and use a reminder if useful. Before travel, arrange sufficient tablets, a prescription copy, storage advice and a plan for time-zone changes. Contact the pharmacy early if you may run out; do not ration doses yourself.

Work, exercise and social activity can often be adjusted around how you feel. Avoid driving or operating machinery if you are dizzy, exhausted, have blurred vision or feel unwell. New breathlessness during familiar activities deserves assessment rather than simply reducing activity.

Let dentists and other clinicians know about treatment and share your oncology contact details. Ask the team before procedures or adding medicines. Do not stop osimertinib for a fixed number of days before surgery unless specifically instructed.

It is reasonable to ask for help with anxiety, sleep, finances or managing tablets. A family member can help keep records, but decisions about doses and restarting treatment should come from the treating team.

Fertility, contraception, pregnancy and breastfeeding

Osimertinib can harm a developing baby. Use effective contraception during treatment. For someone who could become pregnant, US information specifies continuing contraception for 6 weeks after the last dose; European information specifies at least 2 months. For men with a partner who could become pregnant, both specify 4 months after the last dose. Confirm the applicable written plan with your team.

European information warns that oral hormonal contraception may be less reliable. Discuss a suitable method with the team rather than relying on the pill without checking. If pregnancy occurs or is suspected in you or your partner, contact the oncology team promptly for individual advice.

Do not breastfeed during treatment. US information specifies avoiding breastfeeding for 2 weeks after the last dose; European information does not give a fixed interval after stopping. Ask before restarting. If other cancer medicines are involved, their longer contraception or breastfeeding restrictions may determine the final plan.

Animal studies suggest effects on male and female fertility; the effect in humans is uncertain. If having children later matters to you, ask about fertility preservation before treatment begins. Changes in periods or fertility do not provide dependable contraception.

After treatment finishes

Ask for a clear follow-up plan covering scans, blood tests, symptoms and any continuing heart or lung monitoring. Some problems take time to resolve. New breathing symptoms after chest radiotherapy still need assessment, even after osimertinib has stopped. Continue contraception and breastfeeding precautions for the agreed period.

If treatment stopped because of a serious reaction, make sure that reaction is recorded and understood by other clinicians. Do not restart leftover tablets. If it stopped because the cancer changed, the team may discuss further testing and another treatment approach. Your previous benefit or duration on treatment cannot predict another person’s outcome.

Frequently asked questions