Alectinib: ALK-positive lung cancer, dosing, and side effects
Last updated September 7, 2026.
**Alectinib is a targeted cancer medicine called an ALK inhibitor, taken as a capsule by mouth.** Some lung cancers grow because of an abnormal ALK gene that keeps sending a growth signal, and alectinib blocks that signal so the tumor slows or shrinks. It only helps tumors that test positive for an ALK rearrangement, so an FDA-approved test on tumor tissue or blood comes first. The most important safety point is that alectinib can injure the liver, so you need blood tests every 2 weeks for the first 3 months and you should call your care team about yellow eyes, dark urine, or severe pain in the upper right belly.
What does it treat?
Alectinib treats non-small cell lung cancer that tests positive for an ALK gene rearrangement, a subtype that shows up more often in people who never smoked or smoked very little. It is approved for ALK-positive non-small cell lung cancer that has spread beyond the lung, where it is a standard first line targeted therapy and also reaches cancer that has spread to the brain, and for ALK-positive non-small cell lung cancer after surgery to remove the tumor when the tumor was 4 cm or larger or lymph nodes were involved. The symptom patterns that lead to this diagnosis include a cough that will not clear, chest or shoulder pain, coughing up blood, shortness of breath, unexplained weight loss, and sometimes headaches or balance changes when cancer has spread to the brain. Alectinib is taken on its own rather than combined with chemotherapy, and the only brand sold in the US is Alecensa; there are no combination products that contain it.
How do you take it?
Alectinib comes as 150 mg capsules. The usual adult dose is 600 mg, which is four capsules, taken twice a day with food, for a total of 1200 mg a day; that daily total is the ceiling, and no higher dose is approved. Swallow the capsules whole with a meal, and do not open, crush, chew, or dissolve them. If you have severe liver impairment, the label starts you at 450 mg twice a day instead. If you miss a dose, or you vomit after taking one, skip it and take your next dose at the regular time; do not take an extra dose to catch up. When alectinib is given after lung cancer surgery, treatment usually runs for 2 years unless the cancer returns or side effects force a stop. Your doctor may pause treatment or step the dose down to 450 mg or 300 mg twice daily based on blood tests, and alectinib is stopped for good rather than dropped below 300 mg twice daily. Stop taking it and call the same day if you have yellowing of the eyes or skin, dark urine, new or worsening cough or breathlessness, muscle pain with weakness, or a resting pulse that stays under 60 with dizziness.
Side effects to know
- Common: Most people notice constipation, tiredness, muscle aches, mild swelling in the ankles or eyelids, weight gain, rash, and skin that burns quickly in the sun, and routine blood work often shows mild anemia or higher liver enzymes and bilirubin.
- Serious: Stop alectinib and get medical help the same day for signs of liver injury (yellow eyes or skin, dark urine, severe upper right belly pain), lung inflammation (new or worsening cough, breathlessness, or fever), severe muscle pain or weakness with dark urine, or a resting heart rate under 60 with dizziness or fainting. A sharp drop in how much you urinate, with swelling, can signal kidney injury and also needs urgent review.
Who should not take it?
The only listed reason never to take alectinib is a known allergy to it, but several situations need a conversation before you start. Tell your doctor if you have hepatitis or other liver disease, any lung condition such as pulmonary fibrosis, kidney problems, a slow heart rate, or a muscle disorder. Medicines that slow the heart, including beta blockers, verapamil, diltiazem, digoxin, and clonidine, add to alectinib's effect on heart rate, and alectinib can raise blood levels of digoxin, dabigatran, rosuvastatin, and methotrexate, so those doses may need adjusting. Alectinib can harm a developing baby: if you can become pregnant, use effective nonhormonal birth control during treatment and for 1 week after your final dose, and if you are male with a partner who can become pregnant, use condoms during treatment and for 3 months after your final dose. Do not breastfeed during treatment or for 1 week after the final dose. The label sets no alcohol limit, but keep alcohol light or skip it while your liver tests are being monitored, since alectinib already puts stress on the liver. Alectinib also makes skin burn faster, so use broad-spectrum sunscreen with SPF 50 or higher, use lip balm, and cover up outdoors during treatment and for 7 days after your last dose.
When is it an emergency?
Call 911 if you collapse or faint, have trouble breathing or chest pain, or have swelling of the face, lips, or tongue with hives, which can mean a severe allergic reaction. Call Poison Control at 1-800-222-1222 if you or anyone else takes extra alectinib capsules or a child swallows any; there is no antidote, so care is supportive and starting early matters. Get same-day medical care for yellowing of the eyes or skin, dark or cola colored urine, severe pain in the upper right belly, a new fever with cough or breathlessness, muscle pain with real weakness, passing much less urine than usual, or a resting pulse that stays under 60 with dizziness.
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Common questions
What is the maximum dose of alectinib?
The approved adult dose is 600 mg twice a day, which is four 150 mg capsules each time and 1200 mg total per day. That is the ceiling, and taking more does not treat the cancer better while it does raise the chance of liver, muscle, and heart rate problems. If you have severe liver impairment, the label lowers the starting dose to 450 mg twice a day. Your doctor may also step you down to 450 mg or 300 mg twice a day if blood tests or side effects call for it, and alectinib is stopped rather than reduced below 300 mg twice a day.
Do I take alectinib with food?
Yes, take every dose with food. Food increases how much of the drug your body absorbs, and the 600 mg twice daily dosing in the label assumes a meal each time. Swallow the capsules whole and do not open, crush, chew, or dissolve them. If you vomit shortly after a dose, do not take a replacement; wait and take your next scheduled dose with food.
What if I miss a dose or take too many capsules?
If you miss a dose, skip it and take the next one at its usual time. Do the same if you throw up after a dose, and never double up to make up for a missed one. If extra capsules are swallowed by you or by anyone else, including a child, call Poison Control at 1-800-222-1222 right away. There is no specific antidote for alectinib, so treatment is supportive and focuses on watching the liver, kidneys, muscles, and heart rate. Call 911 instead if the person faints, cannot breathe, or is not responding.
Can I drink alcohol while taking alectinib?
The label does not ban alcohol, but the caution is real because the risks add up. Alectinib can raise liver enzymes and, less often, cause serious liver injury, and alcohol pushes the liver in the same direction. The practical approach is an occasional drink at most, and none at all during the first 3 months while your liver tests are being checked every 2 weeks. If your ALT, AST, or bilirubin come back high, stop alcohol completely until your oncology team tells you otherwise.
Is alectinib safe during pregnancy or breastfeeding?
No. Alectinib can harm a developing baby based on how it works and on animal studies, so it is not used during pregnancy, and your doctor will confirm you are not pregnant before you start. If you can become pregnant, use effective nonhormonal birth control during treatment and for 1 week after your final dose, since hormonal methods may not be reliable. Men with a partner who can become pregnant should use condoms during treatment and for 3 months after the final dose. Do not breastfeed during treatment or for 1 week after your last dose. Tell your doctor right away if you become pregnant while taking it.
What medicines and supplements interact with alectinib?
Alectinib usually does not need a dose change for drugs that block or speed up CYP3A enzymes, so many antibiotics and antifungals can be used, but your team still needs your full medicine list before deciding. The bigger issue is anything that slows the heart, such as beta blockers, verapamil, diltiazem, digoxin, and clonidine, because alectinib can slow your pulse further. Alectinib also blocks the P-gp and BCRP transporters, which can raise blood levels of digoxin, dabigatran, rosuvastatin, and methotrexate. Include over the counter products and supplements, especially St. John's wort, and check with your team before starting anything new.