Kadcyla (ado-trastuzumab emtansine) is a prescription brand-name medication. The Food and Drug Administration (FDA) has approved it to treat metastatic or early breast cancer that’s HER2-positive (HER+) in certain situations. Kadcyla is approved for use in adults.

Here are some fast facts about Kadcyla:

  • Active ingredient: ado-trastuzumab emtansine
  • Drug class: antibody-drug conjugate, a type of biologic medication
  • How it’s given: as an IV infusion by a healthcare professional

For metastatic breast cancer, Kadcyla is typically given long term over several treatment cycles. (Each treatment cycle is 3 weeks long.) For early HER+ breast cancer, Kadcyla is given for up to 14 treatment cycles. You and your doctor will decide how long you’ll receive Kadcyla. It may depend on how your body responds to the medication and what side effects you may have.

Similar to other drugs, Kadcyla can cause side effects. Read on to learn about potential common, mild, and serious side effects. For a general overview of Kadcyla, including details about its uses, see this article.

Kadcyla can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Kadcyla in clinical trials:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Kadcyla use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to Kadcyla’s prescribing information.

Mild side effects that have been reported with Kadcyla include:

These side effects may be temporary, lasting a few days to weeks. But if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Kadcyla and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Kadcyla may cause serious side effects in some people. The list below may not include all possible serious side effects of the drug. For more information, you can refer to Kadcyla’s prescribing information.

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

Serious side effects that have been reported and their symptoms include:

* For more information about this side effect, see “Side effect specifics” below.
† Kadcyla has a boxed warning about the risk of this side effect. This is a serious warning from the Food and Drug Administration (FDA).
‡ Kadcyla has a boxed warning about this. To learn more, see “Pregnancy and breastfeeding while taking Kadcyla” in the “Precautions for Kadcyla” section below.

Kadcyla may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

How long do Kadcyla’s side effects last?

Since everyone’s body is unique, each person who’s prescribed Kadcyla will experience their treatment differently. So, it isn’t always possible to predict whether you’ll have side effects or how long they’ll last.

The more common side effects seen in Kadcyla’s clinical trials were usually temporary. (For examples of these, see the “More common side effects of Kadcyla” section above.) These symptoms typically eased within a few days or weeks.

Some serious side effects may affect your health long term, even after your treatment ends. Examples include serious heart and liver problems. (For more information, see the “Side effect specifics” section below.)

If you’re having any bothersome side effects, talk with your doctor. They may suggest ways to manage your symptoms. If your symptoms don’t get better within 3 weeks,* your doctor may pause your treatment. Or they may completely stop your treatment if you have severe or serious side effects.

* Kadcyla is typically given once every 3 weeks. For more information about Kadcyla’s dosage and how it’s given, see this article.

Do Kadcyla’s side effects include hair loss?

No, Kadcyla’s side effects don’t usually include hair loss. People taking Kadcyla in clinical trials didn’t report this side effect.

Hair loss from Kadcyla treatment was reported in another trial that compared Kadcyla to the cancer medications Tykerb (lapatinib) and Xeloda (capecitabine). However, hair loss wasn’t a common side effect of any of these treatments.

Other factors may contribute to hair loss, such as:

  • possible stress related to fighting cancer
  • not being able to eat a diet that’s healthy for you due to nausea or drug-related side effects

Talk with your doctor if you’re concerned about hair loss. They may recommend ways to manage stress or suggest talking with a dietitian.

Are Kadcyla’s side effects similar to side effects of chemotherapy?

Not usually. In general, people usually tolerate Kadcyla treatment much better than chemotherapy. This is because Kadcyla is meant to target specific cancer cells, while chemotherapy targets all cells that grow rapidly. This may include some healthy cells. So certain side effects may be more common and severe with chemotherapy.

For example, vomiting is a very common side effect of chemotherapy drugs, such as cisplatin. Nearly all people who take cisplatin have vomiting, and it’s often severe. To help prevent vomiting, cisplatin treatment is almost always prescribed with antiemetic medications (drugs that help reduce nausea or vomiting).

In comparison, vomiting was not a common side effect of Kadcyla. And severe vomiting from Kadcyla treatment was rarely reported.

If you have questions about what side effects to expect from Kadcyla treatment, talk with your doctor.

Learn more about some of the side effects that Kadcyla may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Kadcyla.

Tiredness

Tiredness, also called fatigue, was the most common side effect of Kadcyla treatment in clinical trials.

In fewer cases, fatigue was severe. This led to doctors changing some people’s treatment plans. These changes included reducing the dosage* of Kadcyla or delaying the next dose until the side effect eased.

Keep in mind that cancer itself is a common cause of fatigue. And Kadcyla is prescribed to treat certain types of breast cancer.

What you can do

The following tips may be helpful in managing tiredness during your Kadcyla treatment:

  • Be sure to get plenty of rest. This includes aiming for a full night’s sleep and taking naps during the day when you need to.
  • Try to be active. A moderate amount of daily exercise, such as taking a walk, can give you an energy boost.
  • Make sure to maintain a diet that’s healthy for you. To ensure you’re consuming enough food to fuel your body, try using a calorie-tracking app. You can also talk with your doctor or a dietician about which foods are better for you while you’re receiving cancer treatment.

If you have questions about tiredness with Kadcyla treatment, talk with your doctor or pharmacist.

* For more information about Kadcyla’s dosage, see this article.

Bleeding

Kadcyla treatment may increase the risk of bleeding. Periods of internal bleeding commonly occurred in people who received Kadcyla in clinical trials. Rarely, serious hemorrhages (bleeding that’s hard to stop) in the digestive tract, lungs, and brain have been reported. One case was fatal.

Symptoms of bleeding may include:

Certain factors may increase your risk of bleeding during Kadcyla treatment. These include whether you have thrombocytopenia (low platelet count) or if you take anticoagulant or antiplatelet drugs (blood thinners). However, periods of bleeding can still occur in people who receive Kadcyla and don’t have these risk factors.

What you can do

Tell your doctor right away or seek immediate medical attention if you develop any symptoms of bleeding.

Before you start Kadcyla treatment, be sure to tell your doctor and pharmacist about all of the medications that you take. This includes dietary supplements and over-the-counter drugs. They’ll check if any of these could increase your risk of bleeding. If so, they’ll monitor you closely during Kadcyla treatment. Your doctor will also monitor your platelet counts using blood tests before and during your treatment.

Peripheral neuropathy

Kadcyla may cause peripheral neuropathy (a condition in which your nerves become damaged). This side effect was common in people who took Kadcyla in clinical trials.

Peripheral neuropathy causes certain symptoms, particularly in your arms, hands, legs, and feet. These include:

Peripheral neuropathy from Kadcyla treatment is usually mild or manageable. However, in some cases, it can be severe. In trials, some people had to pause, reduce, or stop their treatment due to this side effect.

What you can do

If you develop bothersome symptoms of peripheral neuropathy, talk with your doctor. They may have you temporarily stop Kadcyla treatment. And then they may restart the treatment with a lower dosage. They may also recommend ways to ease your symptoms. Physical therapy and certain medications, such as Neurontin (gabapentin) may be helpful.

If your symptoms don’t improve or become severe, tell your doctor. They may stop Kadcyla treatment permanently. And they may suggest other treatment options for you to consider.

Severe heart problems

Taking Kadcyla may lead to severe heart problems, such as decreased heart function, and congestive heart failure (CHF). With CHF, your heart can’t pump blood efficiently. Kadcyla has a boxed warning about the risk of this side effect. This is a serious warning from the Food and Drug Administration (FDA). It alerts patients and doctors about drug effects that could be dangerous.

Symptoms of heart problems to watch for include:

It isn’t known for sure, but Kadcyla may not be safe for people who already have heart problems. These include people with CHF, serious heart rhythm problems, and recent heart attack, or unstable angina (a type of chest pain).

What you can do

Tell your doctor immediately if you have symptoms of CHF. If they confirm you have CHF, your doctor will likely have you stop Kadcyla treatment. They’ll talk with you about other treatment options.

If you already have a heart problem or had a heart attack in the past, talk with your doctor before starting Kadcyla treatment. If they determine the drug is safe for you, they’ll likely monitor you very closely during treatment.

Your doctor will check the health of your heart before and during Kadcyla treatment. They’ll check this by measuring the amount of blood your heart can pump. This measurement is called the left ventricular ejection fraction (LVEF). If your LVEF declines and doesn’t get better, your doctor will stop Kadcyla treatment.

Severe liver problems

Kadcyla treatment may cause severe liver problems in some people. Liver damage from Kadcyla can be severe and, rarely, lead to death. In fact, Kadcyla has a boxed warning about the risk of this side effect. This is a serious warning from the Food and Drug Administration (FDA). It alerts patients and doctors about drug effects that could be dangerous.

Symptoms of liver damage can include:

In rare cases, a rare liver disease called nodular regenerative hyperplasia (NRH) was reported in Kadcyla’s clinical trials. With NRH, you have noncancerous changes in your liver that may lead to portal hypertension (high blood pressure in the liver).

In these trials, it was common for people to have increases in liver enzymes. Increased liver enzymes can sometimes be a sign of liver problems. However, in many cases, your liver enzymes will return to healthy levels over time.

What you can do

Your doctor will likely check your liver health using a liver function test before and during Kadcyla treatment. This will help your doctor monitor for possible liver problems.

If you develop symptoms of liver damage during your treatment with Kadcyla, tell your doctor right away. Depending on the type and severity of the liver problem, they may pause or permanently stop treatment.

Allergic reaction

As with most drugs, Kadcyla can cause an allergic reaction in some people.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • swelling under your skin, typically in your lips, eyelids, feet, or hands
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What you can do

For mild symptoms of an allergic reaction, call your doctor right away. They may recommend ways to ease your symptoms and determine whether you should keep taking Kadcyla. But if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Kadcyla comes with several warnings and precautions.

Boxed warnings

This drug has boxed warnings about risks of severe heart problems, fetal harm, and severe liver problems. These are serious warnings from the Food and Drug Administration (FDA).

For more information about heart and liver problems, see the “Side effect specifics” section above. For details about the risk of fetal harm, see “Pregnancy and breastfeeding while taking Kadcyla” below.

Other precautions

Be sure to talk with your doctor about your health history before you take Kadcyla. This drug may not be the right treatment for you if you have certain medical conditions or other factors that affect your health. The conditions and factors to consider include:

Heart problems. Kadcyla may cause heart problems. If you already have a medical condition that affects your heart or have ever had a heart attack, talk with your doctor. If they determine your heart is healthy enough, they may prescribe you Kadcyla and they’ll monitor you closely during your treatment. If your heart condition gets worse, they’ll likely have you stop treatment.

Allergic reaction. If you’ve had an allergic reaction to Kadcyla or any of its ingredients, your doctor will likely not prescribe the drug. Ask your doctor what other medications may be better options for you.

Alcohol use with Kadcyla

Alcohol isn’t known to interact with Kadcyla.

However, heavy alcohol use can lead to liver problems. Kadcyla may also cause liver problems* as a rare but severe side effect. So, it’s possible that drinking alcohol, especially excessive drinking, could raise your risk of liver problems during Kadcyla treatment.

If you drink alcohol, talk with your doctor about how much, if any, is safe for you to consume during Kadcyla treatment.

* Kadcyla has a boxed warning about the risk of this side effect. This is a serious warning from the Food and Drug Administration (FDA). To learn more, see “Side effect specifics” above.

Pregnancy and breastfeeding during Kadcyla treatment

Below is information about pregnancy and breastfeeding during Kadcyla treatment.

Pregnancy

Kadcyla is not safe to receive during pregnancy. So, you should not receive Kadcyla if you’re pregnant or planning to become pregnant. Kadcyla treatment during pregnancy may cause congenital anomalies (commonly called “birth defects”) and pregnancy loss. In fact, Kadcyla has a boxed warning about these risks. A boxed warning is the strongest type of warning from the Food and Drug Administration (FDA). Boxed warnings alert patients and healthcare professionals about drug effects that could be dangerous.

This warning is based on reports of fetal development problems and pregnancy loss in people who took Herceptin (trastuzumab) during pregnancy. Kadcyla’s active ingredient, ado-trastuzumab, is similar to this drug. Kadcyla also contains emtansine, a drug that may be harmful to a fetus based on how it works.

If you’re able to become pregnant, your doctor will give you a pregnancy test before prescribing you Kadcyla. This is to confirm that you’re not pregnant before you start treatment. If you become pregnant while receiving Kadcyla treatment, or within 7 months after your treatment ended, tell your doctor right away.

You’re also encouraged to report your pregnancy to a pregnancy registry. These registries help medical professionals collect information about the safety of certain drugs. This information can help people make informed decisions about having certain treatments during pregnancy. You can learn more by talking with your doctor or calling the Kadcyla Pregnancy Exposure Registry at 888-835-2555.

If you or your partner can become pregnant, be sure to talk with your doctor about your birth control needs. If you’re female,* you should use birth control during Kadcyla treatment and for at least 7 months after treatment. And if you’re male,* you should use birth control during treatment and for at least 4 months after your last dose. Talk with your doctor if you have questions about your birth control needs.

* Sex and gender exist on spectrums. Use of the term “female” and “male” in this article refers to sex assigned at birth.

Breastfeeding

Kadcyla is not safe to receive while you’re breastfeeding. Your doctor will not recommend breastfeeding until at least 7 months after your treatment ends.

Talk with your doctor about other healthy ways to feed your child during this time.

Kadcyla’s more common side effects are usually mild. However, serious side effects are possible.

If you’d like to learn more about Kadcyla, talk with your doctor or pharmacist. They can help answer any questions you have about side effects from taking the drug.

Besides talking with your doctor, you can do some research on your own. These articles might help:

Disclaimer: Medical News Today 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.