Neratinib (Nerlynx)

Neratinib at a glance

Nerlynx contains neratinib, an oral tyrosine kinase inhibitor. The reviewed tablets contain 40 mg each. The usual full daily dose is 240 mg, taken as six tablets together with food. Some prescriptions start lower and increase over two weeks; others require a lower dose because of side effects or other clinical factors. Follow your own written prescription.

Neratinib may be prescribed alone or, in some treatment settings, with capecitabine. The two medicines have different calendars and precautions. Neither should be added, omitted or adjusted without instructions. The name of a combination does not mean all its tablets are taken on the same days.

The most important practical concerns are diarrhoea, dehydration, liver problems and interactions with other medicines. Regular tests are needed even when you feel well. Side effects do not measure how well treatment is working.

What neratinib is and how it works

Cells use proteins called receptors to receive signals that influence growth. HER2 is one such receptor. Some cancer cells produce too much HER2, or have extra copies of its gene, which can make this signalling unusually active. Neratinib blocks the working part of HER2 inside cells, along with related proteins called EGFR and HER4.

These proteins are kinases: they help pass instructions between other proteins. Blocking their activity can interfere with the growth of susceptible cancer cells. Neratinib is different from a HER2-targeted antibody, which acts through a different type of medicine. It is also different from checkpoint immunotherapy.

Targeted treatment can affect healthy tissues, including the bowel and liver. “Targeted” therefore does not mean free of significant side effects. A treatment plan balances likely benefit against these risks for the individual person.

How the team decides whether it is suitable

Your oncologist considers the exact diagnosis, HER2 test results, hormone-receptor results where relevant, previous treatment, time since previous treatment and your overall health. A report describing HER2 overexpression or gene amplification helps guide selection. A different genetic finding involving HER2 should not automatically be treated as equivalent.

Tell the team about ongoing diarrhoea, inflammatory bowel problems, difficulty absorbing food or medicines, liver disease, kidney disease and heart problems. Explain any previous reaction to neratinib or tablet ingredients; known allergy is a reason not to use it under European guidance. Older people can be particularly vulnerable to the consequences of diarrhoea, so practical support and early reporting matter.

Severe liver impairment is an important regional difference. The US label specifies a reduced starting dose of 80 mg daily for severe impairment; the European label says neratinib must not be used in this situation. European information also does not recommend treatment in severe kidney impairment or dialysis. These are specialist prescribing decisions, not reasons to choose a dose yourself.

This article describes adult treatment. The reviewed labels do not establish a routine paediatric treatment plan. A child's prescription must never be calculated from these adult examples.

Before treatment starts

Baseline blood tests check liver function, including liver enzymes and bilirubin. Kidney function and blood salts, or electrolytes, help identify risks if fluid is lost through diarrhoea. Your team also considers blood counts and tests required by accompanying treatment. Heart assessment may be appropriate if you have a cardiac history or relevant symptoms.

Bring a complete medicine list, including heartburn remedies, antibiotics, antifungals, supplements and herbal products. An apparently simple change in stomach-acid medicine can substantially reduce neratinib absorption. The pharmacist should review interactions before treatment and again whenever another medicine changes.

Before taking the first tablet, obtain the prescribed diarrhoea medicines and a written prevention and rescue plan. Record your usual number of bowel movements so that changes are easier to explain. Know which symptoms require a call, when to hold treatment if instructed and how to reach your hospital's urgent advice service outside clinic hours.

If capecitabine is planned, ask about assessment for deficiency of dihydropyrimidine dehydrogenase (DPD), an enzyme needed to break down that medicine. The current US capecitabine label calls for testing for relevant DPYD gene variants before starting, unless treatment is immediately necessary. Capecitabine should be avoided in complete DPD deficiency. A reassuring test does not exclude every risk of serious toxicity. This check concerns the accompanying capecitabine, not a test of whether neratinib will work.

Discuss pregnancy prevention and fertility before starting. A pregnancy test is recommended for patients who could become pregnant.

How treatment is taken

Dose, food and the treatment calendar

Take neratinib once daily with food, at roughly the same time each day. European information recommends morning dosing. Swallow tablets whole with water. Do not crush, chew, split or dissolve them; there is no routine home-made liquid or feeding-tube method in the reviewed instructions. If swallowing is difficult, contact the pharmacy before altering a tablet.

The usual full dose is 240 mg daily. A treatment course given alone may be planned for one year, provided treatment remains appropriate and tolerable. The US capecitabine combination uses neratinib on all 21 days of each 21-day cycle, while capecitabine is taken on days 1–14. Do not assume neratinib stops during the capecitabine break.

Starting gradually and preventing diarrhoea

The US label offers a two-week dose-escalation option: 120 mg daily during days 1–7, 160 mg daily during days 8–14, then 240 mg daily from day 15. This is a prescribed starting strategy, not a schedule to introduce yourself after a difficult week. Anti-diarrhoea treatment is used as needed under the accompanying plan.

If this escalation approach is not used, the US label recommends preventive loperamide beginning with the first neratinib dose and continuing through the first 56 days, with further use as needed. The European label describes preventive anti-diarrhoea medicine from the first dose for the first one to two months and does not give the same formal two-week escalation schedule.

Your written instructions should specify the actual loperamide doses, maximum daily amount and what to do if constipation develops. Do not combine different prevention schedules from the internet or take extra doses beyond the agreed limit. Prevention reduces risk but cannot guarantee that severe diarrhoea will not occur.

Missed doses, vomiting and safe storage

If you miss a dose, skip it and take the next dose at the usual scheduled time. Do not double the dose. If you vomit after taking neratinib, do not take replacement tablets; resume with the next scheduled dose and contact the team if vomiting continues.

Keep tablets in their original labelled container, away from children, damp and excessive heat. European instructions specify keeping the bottle tightly closed to protect from moisture; US instructions specify room-temperature storage at 20–25°C (68–77°F), with permitted short excursions described on the label. Follow the pack supplied to you. Keep the moisture-absorbing canister inside the bottle and never swallow it. Return unwanted tablets to a pharmacy using local disposal arrangements.

Monitoring and checking whether treatment is working

Liver tests are required throughout treatment. The US label recommends testing before treatment, monthly for the first three months and every three months afterwards, with extra testing when clinically needed. European information includes testing after one week, monthly for the first three months and every six weeks afterwards. Your clinic will select the schedule appropriate to your prescription and circumstances.

Additional tests may be needed after severe diarrhoea, especially if intravenous fluids are required, or if liver symptoms develop. Kidney function and electrolytes may change during dehydration. A normal result at the last visit does not rule out a new problem.

The team reviews bowel symptoms, fluid intake, weight, appetite and other side effects. If capecitabine is included, its blood-count and other monitoring requirements also apply. Heart pumping-function tests may be considered for people with relevant risk factors rather than automatically following one universal schedule.

Examinations, scans and other disease-specific tests assess benefit according to the treatment goal. A temporary interruption or dose reduction can be needed to control toxicity. It does not automatically mean treatment has failed, but do not restart after a hold until the team confirms the dose and date.

Common side effects and practical management

Diarrhoea and bowel changes

Diarrhoea is especially likely early in treatment, often in the first weeks, although it can develop later. Report changes early and follow the agreed rescue plan. The US patient information advises telling the team about more than two bowel movements in a day or diarrhoea that does not stop; explain how this compares with your normal bowel pattern.

Keep a simple record of loose stools, medicine taken and how much you can drink. Small, frequent drinks may be easier than large amounts. Oral rehydration products can help replace salts if your team recommends them. People with a fluid restriction need an individual plan rather than a general instruction to drink large volumes.

Choose foods you can tolerate. Temporarily reducing foods that worsen symptoms, such as very fatty or spicy meals, may help. Do not rely on dietary changes alone for persistent diarrhoea. Fever, bleeding, marked pain or dehydration needs medical assessment, not simply another anti-diarrhoea tablet.

Loperamide can cause constipation. Report troublesome constipation, and seek prompt advice for a swollen painful abdomen or vomiting. Do not alternate anti-diarrhoea medicines and laxatives without guidance.

Nausea, appetite changes and mouth soreness

Nausea, vomiting, indigestion and abdominal discomfort can occur. Take prescribed anti-sickness medicine as directed and tell the team if it is not helping. Smaller meals may be easier; persistent vomiting or inability to keep fluids down needs prompt advice. Falling weight or prolonged poor intake warrants nutritional support.

Use gentle mouth care and report ulcers or pain that makes eating or drinking difficult. Avoid irritating mouth products. A clinician can check for infection and prescribe suitable treatment rather than assuming every sore mouth is harmless.

Tiredness, skin and nail changes

Balance activity with rest, and report tiredness that suddenly worsens or limits basic tasks. It may reflect treatment, poor intake, dehydration or another cause that needs attention. Gentle activity is reasonable when you feel able.

Dry skin, rash, cracked skin and inflammation around nails can occur. Use a gentle moisturiser and protect sore hands and nails from detergents and repeated friction. Painful, spreading or infected-looking changes should be assessed. In a capecitabine combination, tender red palms or soles may represent hand–foot syndrome from the partner medicine and can require dose changes.

Important serious side effects

Dehydration and kidney injury

Severe diarrhoea can cause rapid fluid and salt loss, low blood pressure and kidney problems. Warning signs include intense thirst, dizziness on standing, marked weakness, fast heartbeat and passing much less urine. Severe or persistent symptoms may require blood tests, intravenous fluids and interruption of treatment.

Contact the team immediately rather than waiting until the next appointment. Do not use dose-adjustment tables as a reason to wait several days before seeking help. Repeated or severe toxicity can lead to permanent discontinuation; the decision depends on the whole regimen and recovery.

Liver injury

Neratinib can raise liver enzymes and sometimes cause significant liver injury. Early changes may only appear in blood tests. Contact the team promptly for yellow skin or eyes, dark urine, pain on the upper right side of the abdomen, unusual fatigue or persistent loss of appetite.

The team may withhold treatment, repeat tests or stop it permanently for severe or recurrent injury. Do not restart because symptoms have settled without confirming the plan. Liver tests are also important after substantial diarrhoea.

Problems related to accompanying treatment

When capecitabine is prescribed, low blood counts, infection, bleeding, heart symptoms and severe skin or bowel toxicity need attention under that medicine's instructions as well. Very early, unexpectedly severe toxicity can be associated with DPD deficiency, even if pre-treatment testing was reassuring. Report it urgently.

Seek emergency care for severe chest pain, major breathing difficulty, collapse or a severe allergic reaction. New breathlessness, swelling or a racing heartbeat also needs prompt assessment, particularly if you have a heart condition. These symptoms should not be dismissed as ordinary treatment fatigue.

Other medicines, supplements and vaccinations

Heartburn and stomach-acid medicines

Neratinib needs an acidic stomach environment for reliable absorption. Proton pump inhibitors, such as omeprazole or lansoprazole, should generally be avoided with it. Separating them by a few hours does not reliably solve the interaction. Arrange an alternative with the prescriber rather than simply stopping necessary stomach protection.

If an H2-receptor blocker is needed, both labels advise taking neratinib at least two hours before, or at least ten hours after, the H2 blocker. For antacids, the US label says to take neratinib at least three hours after the antacid; European instructions require at least three hours of separation. Ask the pharmacist to write an exact timetable for your particular products.

Other interactions

Some medicines change how enzymes and transport proteins handle neratinib. Important examples include certain antifungals, antibiotics, epilepsy medicines and rifampicin. St John's wort can reduce exposure and should not be used. The US and European labels differ in whether particular interacting medicines should be avoided or can be managed with a specialist dose reduction. Do not copy another person's adjusted dose.

Neratinib can also raise exposure to medicines such as digoxin through transport proteins that move drugs through cells. European guidance also recommends monitoring certain medicines, such as rosuvastatin, that use another transport protein. Tell every prescriber and pharmacist about it. If capecitabine is combined with warfarin, the partner medicine requires particular attention to bleeding and anticoagulation monitoring.

Avoid grapefruit and grapefruit juice. European instructions also advise avoiding pomegranate products. Check concentrated fruit or herbal supplements rather than assuming they are safe because they are natural. Discuss vaccinations with the team; suitability, particularly for live vaccines, depends on your whole treatment and immune recovery.

Everyday life during treatment

Plan easy access to a toilet and carry the prescribed rescue medicine when away from home. Travel is often easier once the early diarrhoea pattern is understood. Take sufficient tablets in their original packaging, your medicine list and a plan for obtaining help away from your treating hospital.

Work and activity depend on how you feel. Flexible hours or temporary adjustments can help during the first weeks. Do not drive or operate machinery when tired, dizzy, weak or dehydrated. Avoid pushing through these symptoms to complete a journey.

Tell your dentist and any team planning a procedure about your cancer medicines. There is no universal neratinib stopping interval for every procedure; the treatment team considers the procedure, symptoms and accompanying medicines. Discuss infection precautions and sexual comfort according to your overall treatment. Persistent worry about bowel symptoms or leaving home is worth raising so that support can be arranged.

Fertility, contraception, pregnancy and breastfeeding

Neratinib can harm a developing baby. Use effective contraception during treatment; European guidance specifies a highly effective method. Both reviewed labels specify contraception for patients who could become pregnant for at least one month after the final neratinib dose. European information advises adding a barrier method when hormonal contraception is used because reduced reliability cannot be excluded.

For male patients with partners who could become pregnant, the US label advises effective contraception during treatment and for three months afterwards; European information specifies a barrier method for this period. Contact the team promptly if a pregnancy occurs or is suspected.

Accompanying medicines can require longer precautions. Capecitabine specifies six months after its last dose for female patients and three months for male patients. The team should calculate the final dates from each medicine's actual last dose, rather than applying neratinib's shorter female interval to the whole combination.

Do not breastfeed while taking neratinib. The US label specifies avoiding breastfeeding for at least one month after the last dose; European information requires an individual decision about breastfeeding and treatment and does not give the same fixed interval. The breastfeeding plan must also cover capecitabine or any other accompanying treatment. Obtain explicit advice before restarting. Human fertility effects are uncertain; discuss preservation options and the effects of the complete treatment plan before starting where possible.

After treatment finishes

Keep follow-up appointments and report persistent diarrhoea, liver symptoms or other new problems after stopping. Blood tests may continue until abnormalities have resolved. Do not restart leftover tablets if symptoms or scan findings worry you. A new treatment decision requires clinical review.

Continue contraception and breastfeeding precautions for the agreed period. Ask the pharmacist when interacting medicines can be changed back, and return unused tablets safely. Finishing a planned course does not remove the need for ongoing disease-specific follow-up.

Frequently asked questions