Afatinib: what it treats, how to take it, side effects
Last updated September 7, 2026.
**Afatinib is a prescription cancer medicine in the tyrosine kinase inhibitor class.** It blocks signals that help certain cancer cells grow and multiply. Report diarrhea promptly to your oncology team because severe or persistent diarrhea can cause dehydration and kidney failure.
What does it treat?
You may receive afatinib, sold as Gilotrif, for non-small cell lung cancer that has spread to other parts of your body. It is approved as initial treatment when an FDA-approved tumor test identifies certain EGFR gene changes that respond to afatinib. It also treats metastatic squamous non-small cell lung cancer that has worsened after platinum-based chemotherapy. Your oncologist uses your tumor results and treatment history to decide whether it fits your cancer.
How do you take it?
Afatinib comes as 20 mg, 30 mg, and 40 mg tablets. The usual adult dose is 40 mg by mouth once daily; the labeled starting dose for severe kidney impairment is 30 mg daily. Your daily ceiling is your prescribed dose: the US label does not give one universal maximum and allows specialist adjustments for certain interactions. Take it at least 1 hour before or 2 hours after food. Take a missed dose when remembered unless your next dose is within 12 hours; then skip it and never double up. Stop taking it and call your oncology team immediately for severe diarrhea, diarrhea lasting at least 2 days despite prescribed diarrhea medicine, or the serious symptoms below.
Side effects to know
- Common: You may develop diarrhea, an acne-like rash, mouth sores, dry or itchy skin, inflammation around your nails, reduced appetite, nausea, or vomiting.
- Serious: Stop afatinib and get medical help immediately for blistering or peeling skin, new or worsening cough or fever, yellow skin or eyes, painful red eyes or vision changes, or new leg swelling with a racing heartbeat. Severe diarrhea with little urine can signal dehydration or kidney injury; breathing trouble or severe abdominal pain needs emergency care.
Who should not take it?
Before treatment, tell your oncologist about any afatinib allergy, kidney or liver disease, other lung disease, heart problems, eye problems or contact lenses, stomach ulcers, bowel perforation, or diverticular disease. Review every medicine and supplement, especially rifampin, seizure medicines, ritonavir, certain antifungals, St. John's wort, corticosteroids, and NSAIDs such as ibuprofen. Afatinib can harm an unborn baby: discuss pregnancy before treatment, use effective birth control during treatment and for at least 2 weeks afterward, and report pregnancy immediately. Do not breastfeed during treatment or for 2 weeks after your last dose. The label gives no specific alcohol limit; ask your oncology team before drinking and avoid alcohol during diarrhea, dehydration, or mouth sores.
When is it an emergency?
For an overdose or extra dose, call Poison Control at 1-800-222-1222 immediately, even without symptoms. Overdose symptoms include nausea, vomiting, weakness, dizziness, headache, and abdominal pain. Call 911 for collapse, breathing trouble, inability to wake up, or throat or tongue swelling suggesting a severe allergic reaction. Go to an emergency department for severe abdominal pain, extensive blistering or peeling skin, or severe diarrhea with faintness or very little urine.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
What is the maximum daily dose of afatinib?
The usual labeled adult dose is 40 mg once daily. The US label does not specify a single maximum for everyone. It permits a 10 mg daily increase, as tolerated, when certain medicines that lower afatinib exposure must be taken long term. Only your oncologist should make that adjustment; never exceed your prescribed daily dose.
Can I drink alcohol while taking afatinib?
The FDA label does not set an alcohol limit or describe a specific alcohol interaction. Ask your oncology team whether drinking fits your liver health and other medicines. Avoid alcohol when you have diarrhea, dehydration, or mouth sores because it can worsen these problems.
Can I take afatinib while pregnant or breastfeeding?
Afatinib can harm your unborn baby, so discuss pregnancy plans with your oncologist before treatment. Use effective birth control during treatment and for at least 2 weeks after your last dose. Call your oncology team immediately if you become pregnant or think you are pregnant. Do not breastfeed during treatment or for 2 weeks after your last dose.
Do I take afatinib with food, and what if I miss a dose?
Take afatinib on an empty stomach, at least 1 hour before or 2 hours after a meal or snack. Aim for the same time each day. If you forget a dose, take it when you remember unless your next dose is within 12 hours. In that case, skip it and resume your regular schedule without doubling the dose.
What are the signs of an afatinib overdose?
Too much afatinib can cause nausea, vomiting, weakness, dizziness, headache, or abdominal pain. Call Poison Control at 1-800-222-1222 immediately after an extra dose or suspected overdose, even if you feel well. Have your medication bottle and the amount and time taken ready. Call 911 for collapse, breathing trouble, a seizure, or inability to wake up.
Which medicines interact with afatinib?
Ritonavir, itraconazole, verapamil, and some other medicines can increase afatinib levels and side effects. Rifampin, carbamazepine, phenytoin, and St. John's wort can lower its levels and effectiveness. Corticosteroids and NSAIDs such as ibuprofen can increase the risk of a tear in your stomach or intestine. Have your oncology pharmacist check prescriptions, nonprescription medicines, and supplements before you start or stop them.