Alecensa (alectinib) is a prescription drug that’s used to treat a type of lung cancer. Alecensa can cause side effects that range from mild to serious. Examples include fatigue, constipation, and anemia.

Specifically, Alecensa is used in adults to treat a certain type of non-small cell lung cancer (NSCLC). The NSCLC must be both:

The active ingredient in Alecensa is alectinib. (An active ingredient is what makes a drug work.) The drug comes as a capsule that you swallow.

Keep reading to learn about the common, mild, and serious side effects that Alecensa can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects during their Alecensa treatment.

Examples of Alecensa’s commonly reported side effects include:

* To learn more about this side effect, see “Changes in certain blood tests” in the “Side effects explained” section below.

Mild side effects have been reported with Alecensa. These include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. Do not stop taking Alecensa unless your doctor recommends it.

Alecensa may cause mild side effects other than those listed above. See the Alecensa prescribing information for details.

Serious side effects can happen with Alecensa. Some of these side effects are more common, while others are rare.

Serious side effects that have been reported with Alecensa include:

If you develop serious side effects while taking Alecensa, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Alecensa. But this side effect wasn’t reported in studies.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Alecensa, visit MedWatch.

Learn more about some of the side effects Alecensa may cause.

Mouth sores

Mouth sores are a rare side effect of Alecensa. These sores may appear as small blisters or cuts and can affect your:

  • tongue
  • gums
  • cheeks
  • inside of your lips

Other symptoms that can occur with mouth sores include:

  • swelling
  • peeling
  • stinging or burning sensation

What might help

Tell your doctor if you have painful or bothersome mouth sores while taking Alecensa. They can suggest ways to manage this side effect. For example, they may recommend over-the-counter creams or other medications that can help relieve your discomfort.

Changes in certain blood tests

It’s common for Alecensa to cause changes in certain blood tests. This includes tests that check your levels of:

Alecensa may cause any of the following changes:

Alecensa may also cause changes in blood tests that check your kidney function or liver function. Changes in these tests can be a sign of a kidney or liver problem. These are possible serious side effects of Alecensa.

What might help

Your doctor will likely give you blood tests before you start Alecensa and often during treatment.

If you have symptoms of the conditions above while taking Alecensa, tell your doctor right away. They’ll likely check your blood test results and suggest ways to ease your symptoms. They’ll advise if it’s safe for you to keep taking Alecensa or if you need a lower dosage of the drug.

Vision problems

Vision problems are a less common side effect of Alecensa. Examples of vision problems this drug may cause include:

What might help

If you’re concerned about vision problems with Alecensa, talk with your doctor. They can suggest ways to manage these side effects. They’ll also advise if it’s safe for you to keep taking Alecensa.

Allergic reaction

Like most drugs, Alecensa can cause an allergic reaction in some people. But this side effect wasn’t reported in studies.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you swallow, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Alecensa, they’ll decide if you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Alecensa, they may have you switch to a different treatment.

Keeping track of side effects

During your Alecensa treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Taking notes and sharing them with your doctor will help them learn more about how Alecensa affects you. They can then use this information to adjust your treatment plan if needed.

Get answers to some frequently asked questions about Alecensa’s side effects.

Does Alecensa cause hair loss?

No, it’s not likely. Hair loss wasn’t reported as a side effect in studies of Alecensa.

But cancer treatments other than Alecensa may cause this side effect. For example, chemotherapy drugs are known to cause hair loss.

If you’re concerned about hair loss with Alecensa or other cancer treatments you may be receiving, talk with your doctor. They can advise you on your risk of this side effect. And your doctor can recommend ways to manage hair loss if it happens.

Can Alecensa cause bleeding problems?

No, Alecensa isn’t known to cause bleeding problems. This side effect wasn’t reported in studies of the drug.

But certain bleeding problems, such as bleeding more easily than usual, can be a sign of liver problems. And liver problems are a possible serious side effect of Alecensa.

Other possible symptoms of liver problems include:

If you have bleeding problems while taking Alecensa, tell your doctor right away. Also tell them if you have other symptoms of liver problems. They’ll likely give you blood tests to check how well your liver is working.

Your doctor may also check for other causes of bleeding problems. They’ll let you know if it’s safe for you to keep taking Alecensa.

Does Alecensa cause nerve damage?

No, it’s not likely. Nerve damage wasn’t reported as a side effect in studies of Alecensa.

But other cancer therapies are known to cause nerve damage. For example, chemotherapy may cause peripheral neuropathy. This refers to nerve damage that leads to weakness, numbness, or pain. These symptoms typically affect the arms, hands, legs, or feet.

Tell your doctor if you’re concerned about nerve damage with Alecensa or other cancer treatments. They can talk with you about your risk of this side effect. And they’ll tell you what to do if you have any symptoms of nerve damage.

Alecensa may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before starting Alecensa. The items below are some of the factors to consider.

Lung problems. Before taking Alecensa, be sure to tell your doctor about any lung or breathing problems you have. Alecensa may cause certain lung problems, such as swelling in your lungs or pneumonia. And these side effects could worsen your condition. Your doctor can tell you if it’s safe to take Alecensa.

Severe liver or kidney problems. Before taking Alecensa, tell your doctor about any severe liver or kidney problems you have. Alecensa hasn’t been studied in people with these conditions, so it’s not known if this drug is safe for them. Alecensa can also cause liver or kidney problems as a side effect, which may worsen your condition. Your doctor will advise you on whether or not Alecensa is right for you.

Slow heart rate. Tell your doctor if you have a slow heart rate before starting Alecensa. This drug may cause a slow heart rate as a side effect, which could worsen your condition. While you’re taking Alecensa, your doctor will monitor your heart rate from time to time. If you have a severely slow heart rate, they may have you stop taking the drug until your heart rate increases. Or they may prescribe a drug other than Alecensa for you.

Allergic reaction. If you’ve had an allergic reaction to Alecensa or any of its ingredients, your doctor will likely not prescribe it for you. Ask your doctor what other medications are better options.

Alcohol and Alecensa

There aren’t any known safety issues with drinking alcohol in moderation while taking Alecensa.

But keep in mind that drinking large amounts of alcohol can damage your liver. It isn’t known whether Alecensa is safe for people with liver damage. And Alecensa may cause liver problems as a side effect, which could worsen liver damage.

If you drink alcohol, talk with your doctor about the amount that’s safe for you to drink while taking Alecensa.

Pregnancy and breastfeeding while taking Alecensa

Below are details about taking Alecensa while pregnant or breastfeeding.

Alecensa and pregnancy

It’s recommended that you avoid taking Alecensa while pregnant. The drug may cause harm to a fetus if taken during pregnancy.

If you or your partner can become pregnant, you should use an effective form of birth control while taking Alecensa. Females* should continue to use birth control for at least 1 week after their last dose of the drug. And males* should continue to use birth control for at least 3 months after their last dose.

If you’re pregnant or planning a pregnancy, talk with your doctor before starting Alecensa. They may recommend a different drug for your condition.

* In this article, we use the terms “female” and “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Alecensa and breastfeeding

It’s recommended that you avoid breastfeeding while taking Alecensa. If taken while breastfeeding, the drug may pass into your breast milk. And this could cause side effects in a child who’s breastfed.

To be safe, you should avoid breastfeeding while taking Alecensa and for at least 1 week after your last dose.

Before starting Alecensa, tell your doctor if you’re breastfeeding or planning to breastfeed. They may discuss other treatment options with you. Or they may suggest other healthy ways to feed your child.

Alecensa is used to treat a certain type of non-small cell lung cancer. Both mild and serious side effects from Alecensa are possible. If you have questions about side effects from Alecensa, talk with your doctor or pharmacist.

Below are a few questions you may want to ask:

  • How do the side effects of Alecensa compare with those of other drugs used to treat lung cancer?
  • Do I have any medical conditions that increase my risk of side effects with Alecensa?
  • Can you recommend treatments for side effects I’m having with Alecensa?

To learn more about Alecensa, see these articles:

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

Q:

Will Alecensa cause delirium or other problems with thinking or understanding?

Anonymous

A:

It isn’t likely. Delirium and other problems with thinking (such as confusion or memory problems) weren’t side effects reported in Alecensa’s studies.

Trouble thinking can be a side effect of certain other drugs sometimes prescribed to people with cancer. For example, opioid pain relievers can cause problems with thinking or understanding. (These are sometimes prescribed for pain relief to people with cancer.)

But Alecensa isn’t known to cause delirium or problems with thinking as side effects.

The Healthline Pharmacist TeamAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.