Kadcyla is a brand-name prescription medication. It’s FDA-approved to treat certain types of HER2-positive (HER2+) breast cancer in adults.

HER2 is a protein involved in cell growth. Cancer cells that have high levels of HER2 are called HER2+. These cancer cells may grow and spread more quickly than typical cancer cells.

Specifically, Kadcyla is used to treat metastatic HER2+ breast cancer. (Metastatic breast cancer is cancer that’s spread from the breast to other parts of the body.) For this use, Kadcyla is prescribed to certain people who’ve already received treatment with trastuzumab (Herceptin) and a taxane chemotherapy drug.

Additionally, Kadcyla is used as an adjuvant therapy* for early HER2+ breast cancer. (Early breast cancer is cancer that hasn’t spread outside the breast tissue or surrounding lymph nodes.) For this use, Kadcyla is prescribed to people who still have cancer cells remaining after neoadjuvanttherapy† with trastuzumab and a taxane.

* Adjuvant therapy is a treatment that’s meant to prevent cancer from returning. With breast cancer, adjuvant therapy usually refers to medications given after surgery to treat any remaining cancer cells.
† Neoadjuvant therapy is a treatment that’s meant to shrink a tumor before undergoing surgery to remove it.

Drug details

Kadcyla, also called T-DM1, is a biologic medication. Biologic medications are made from living cells.

Kadcyla’s active ingredient is ado-trastuzumab emtansine. It’s an antibody-drug conjugate (two molecules that are chemically linked together).

Kadcyla’s antibody component is ado-trastuzumab, which belongs to a group of drugs called HER2-targeted therapies. Kadcyla’s drug component is emtansine, which belongs to a group of chemotherapy drugs called microtubule inhibitors. Emtansine is also called DM1.

Kadcyla comes as a powder inside single-dose vials. It’s mixed with liquid to form a solution. It’s then given as an IV infusion. Your doctor or another healthcare professional will give you Kadcyla at a hospital or doctor’s office.

Kadcyla is available in two strengths: 100 milligrams (mg) and 160 mg.

Effectiveness

For information about the effectiveness of Kadcyla, see the “Kadcyla uses” section below.

Kadcyla’s active ingredient is ado-trastuzumab emtansine. It’s available only as a brand-name biologic medication. Biologic medications are made from living cells.

Kadcyla isn’t currently available in a biosimilar version. A biosimilar drug is “similar” to a brand-name biologic medication. This is because it isn’t possible to make an exact copy of biologic drugs. Biosimilars are considered to be just as safe and effective as the brand-name version.

Kadcyla can cause mild or serious side effects. The following lists contain some of the key side effects that may occur while receiving Kadcyla. These lists do not include all possible side effects.

For more information about the possible side effects of Kadcyla, talk with your doctor or pharmacist. They can give you tips on how to manage any side effects that may be concerning or bothersome.

Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you’d like to notify the FDA about a side effect you’ve had with Kadcyla, you can do so through MedWatch.

Mild side effects

Mild side effects* of Kadcyla can include:

Most of these side effects may go away within a few days or a couple of weeks. But if they become more severe or don’t go away, talk with your doctor or pharmacist.

* This is a partial list of mild side effects from Kadcyla. To learn about other mild side effects, talk with your doctor or pharmacist, or view Kadcyla’s prescribing information.

Serious side effects

Serious side effects from Kadcyla aren’t common, but they can occur. Call your doctor right away if you have serious side effects. Call 911 or your local emergency number if your symptoms feel life threatening or if you think you’re having a medical emergency.

Serious side effects and their symptoms can include:

* For more information about this side effect, see “Side effect details” below.
† Kadcyla has a boxed warning about the risk of this side effect. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.
‡ Kadcyla also has a boxed warning about the risk of fetal harm. For more information about this side effect, see the “Kadcyla and pregnancy” section below.

Side effect details

Here’s some detail on certain side effects this drug may cause.

Liver damage

Some people may develop liver damage* while receiving Kadcyla. Rarely, liver damage from Kadcyla can be severe and lead to death.

Symptoms of liver damage can include:

A few people who received Kadcyla in clinical trials developed nodular regenerative hyperplasia (NRH). This is a rare liver disease that causes noncancerous changes in your liver. In some cases, NRH can lead to non-cirrhotic portal hypertension. With this condition, there’s increased blood pressure in the liver that’s not related to cirrhosis (liver scarring).

In these trials, it was rare for people to have severe liver damage or related symptoms. However, temporary increases of liver enzymes levels were common. Increased liver enzymes can be a sign of liver damage, but not always. Your doctor will likely have you get liver function tests before and during Kadcyla treatment. This is done to monitor the development of possible liver problems.

To learn more about how often this side effect occurred in clinical trials, see the drug’s prescribing information.

If you develop symptoms of liver damage while receiving Kadcyla treatment, tell your doctor right away. And if you have questions about your risk for liver problems, talk with your doctor or pharmacist.

* Kadcyla has a boxed warning about the risk of this side effect. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.

Heart problems

Kadcyla may cause heart problems* in some people. Specifically, Kadcyla treatment may cause changes in the amount of blood your heart can pump.

Doctors can check for this by measuring your left ventricular ejection fraction (LVEF) before and during Kadcyla treatment. (The left ventricle is one of four chambers of the heart. Its job is to pump oxygenated blood to your body.) Your LVEF may decrease while you’re receiving Kadcyla.

These changes in your heart can increase your risk of congestive heart failure (CHF). Symptoms of CHF may include:

If you have heart failure or have had a heart attack or another heart problem, talk with your doctor before starting Kadcyla. Tell your doctor right away if you develop symptoms of heart failure. If your symptoms feel life threatening or you think you’re having a medical emergency, call 911 or your local emergency number.

To learn more about how often this side effect occurred in clinical trials, see the drug’s prescribing information. Or talk with your doctor or pharmacist.

* Kadcyla has a boxed warning about the risk of this side effect. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.

ALLERGIC REACTION

As with most drugs, some people can have an allergic reaction after receiving Kadcyla.

Symptoms of a mild allergic reaction can include:

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:

  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your tongue, mouth, or throat
  • trouble breathing
  • infusion-related reactions that occur during a Kadcyla IV infusion, such as:
    • chills
    • fever
    • chest tightness
    • reduced blood pressure

Call your doctor right away if you have an allergic reaction to Kadcyla, as the reaction could become severe. Call 911 or your local emergency number if your symptoms feel life threatening or if you think you’re having a medical emergency.

Other drugs are available that can treat your condition. Some may be a better fit for you than others. If you’re interested in finding an alternative to Kadcyla, talk with your doctor. They can tell you about other medications that may work well for you.

Note: Some of the drugs listed here are used off-label to treat these specific conditions. Off-label drug use is when a drug that’s approved by the Food and Drug Administration (FDA) is used for a purpose other than what it’s approved for.

Alternatives for treatment of early or metastatic HER2-positve breast cancer

Examples of other drugs that may be used to treat early or metastatic HER2-positive breast cancer* include:

  • trastuzumab (Herceptin)
  • trastuzumab biosimilars (Herzuma, Kanjinti, Ogivri, Ontruzant, and Trazimera)
  • fam-trastuzumab deruxtecan-nxki (Enhertu)
  • pertuzumab/trastuzumab/hyaluronidase-zzxf (Phesgo)
  • pertuzumab (Perjeta)
  • lapatinib (Tykerb)
  • neratinib (Nerlynx)
  • tucatinib (Tukysa)
  • taxane chemotherapy drugs, such as:
    • paclitaxel
    • docetaxel
  • capecitabine (Xeloda)
  • vinorelbine

* For more information about this condition, see the “Kadcyla uses” section below.

You may wonder how Kadcyla compares with other medications that are prescribed for similar uses. To find out how Kadcyla compares to Herceptin, see this article. Talk with your doctor to learn which drug is right for your condition.

Here are answers to some frequently asked questions about Kadcyla.

How long do side effects from Kadcyla last?

It depends on the type of side effects that you have with Kadcyla.

Some side effects, such as infusion-related reactions, go away quickly. This could be within several hours to a day after the IV infusion is stopped.

Other less common side effects of Kadcyla, such as heart problems and liver damage,* may be long term. (For more information about these side effects, see “Kadcyla side effects” above.)

If you’re experiencing side effects from Kadcyla that are lingering or bothersome, tell your doctor. They may recommend ways to manage them.

* Kadcyla has a boxed warning about the risk of these side effects. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.

Is Kadcyla a chemotherapy drug?

Yes and no. Kadcyla contains emtansine (a chemotherapy drug) that’s been chemically linked to ado-trastuzumab (a monoclonal antibody).

Monoclonal antibodies are not chemotherapy drugs. They’re designed to be targeted therapies. (Targeted therapies only affect specific molecules in the body.) So, Kadcyla is considered to be a targeted therapy.

Chemotherapy drugs work by killing all cells in your body that multiply (make more cells) and grow rapidly. This includes both cancer cells and noncancerous cells. (For example, these could include healthy cells of the digestive tract and hair follicles.) As a result, chemotherapy drugs often cause side effects, such as vomiting and hair loss.

Kadcyla is different than chemotherapy because it’s designed to attach to specific targets on HER2-positive (HER2+) cancer cells.* Kadcyla typically causes less harm to healthy cells. However, mild or serious side effects are still possible. (For more information, see “Kadcyla side effects” above.)

If you have questions about Kadcyla or chemotherapy drugs, talk with your doctor.

* For more information about this condition, see the “Kadcyla uses” section below.

Does Kadcyla cause hair loss?

Kadcyla doesn’t cause hair loss in most people who take the drug. And hair loss wasn’t reported as a side effect in Kadcyla’s prescribing information.

In a trial that compared Kadcyla with another cancer treatment, hair loss did occur. But it wasn’t a common side effect with either drug.

Many chemotherapy drugs cause hair loss as a common side effect. But Kadcyla works differently than traditional chemotherapy drugs. Kadcyla is designed to attach to specific targets on certain breast cancer cells.

If you have questions about hair loss while receiving cancer treatment, talk with your doctor or pharmacist.

Does Kadcyla cure breast cancer?

There’s no known cure for cancer, but some treatments may help you reach remission. With remission, you’ll have lessened signs and symptoms from your cancer.

If you have early breast cancer, Kadcyla may lower the chance of your cancer coming back. (Early breast cancer is cancer that hasn’t spread outside the breast tissue or surrounding lymph nodes.) This was observed in clinical trials of people who received Kadcyla for early HER2+ breast cancer.*

If you have metastatic breast cancer, Kadcyla may help your cancer stop growing and spreading. (Metastatic breast cancer is cancer that’s spread from the breast to other parts of the body.) It may also help you live longer. These outcomes were seen in people with metastatic HER2+ breast cancer* who received Kadcyla treatment in clinical trials.

To learn more about treatments for your type of breast cancer, talk with your doctor.

* For more information about this condition, see the “Kadcyla uses” section below.

As with all medications, the cost of Kadcyla can vary.

The actual price you’ll pay depends on your insurance plan and your location.

Before approving coverage for Kadcyla, your insurance company may require you to get prior authorization. This means that your doctor and insurance company will need to communicate about your prescription before the insurance company will cover the drug. The insurance company will review the prior authorization request and decide if the drug will be covered.

If you’re not sure if you’ll need to get prior authorization for Kadcyla, contact your insurance company or Medicare plan.

Financial and insurance assistance

If you need financial support to pay for Kadcyla, or if you need help understanding your insurance coverage, help is available.

Genentech USA, Inc, the manufacturer of Kadcyla, offers a few programs to help lower the cost of their drug. For more information and to find out if you’re eligible for support, call 877-GENENTECH (877-436-3683). Or you can visit the manufacturer’s website.

To learn more about saving money on prescriptions, check out this article.

Generic or biosimilar version

Kadcyla’s active ingredient is ado-trastuzumab emtansine. It’s available only as a brand-name biologic medication. Biologic medications are made from living cells.

Kadcyla isn’t currently available in a biosimilar version. A biosimilar drug is “similar” to a brand-name biologic medication. This is because it isn’t possible to make an exact copy of biologic drugs. Biosimilars are considered to be just as safe and effective as the brand-name version.

The Food and Drug Administration (FDA) approves prescription drugs such as Kadcyla to treat certain conditions. Kadcyla may also be used off-label for other conditions. Off-label drug use means using a drug for a purpose other than what it’s been approved for by the FDA.

Kadcyla is FDA-approved to treat certain types of HER2-positive (HER2+) breast cancer in adults.

HER2 is a protein involved in cell growth. Cancer cells that have unusually high amounts of HER2 are called HER2+. These cancer cells may grow and spread more quickly than typical cancer cells. To check if Kadcyla may be right for you, your doctor will test your breast cancer for HER2.

The types of HER2+ positive breast cancer that Kadcyla is approved to treat are described below.

To learn more about managing and treating breast cancer, you can also check out Medical News Today’s breast cancer hub.

Kadcyla for treatment of metastatic breast cancer

Kadcyla is approved to treat HER2+ metastatic breast cancer in certain people. Metastatic breast cancer is cancer that’s spread from the breast to other parts of the body.

For this use, Kadcyla is prescribed to people who were already given certain drugs to treat early or metastatic breast cancer. (Early breast cancer is cancer that hasn’t spread outside the breast tissue or surrounding lymph nodes.) These drugs include trastuzumab (Herceptin) and a taxane chemotherapy drug. And they could have been given separately or together as a combination.

Kadcyla is given to those who’ve either:

  • received past treatment for metastatic cancer, or
  • had their cancer get worse or come back during or within 6 months of finishing adjuvant therapy*

* Adjuvant therapy is a treatment that’s meant to prevent cancer from returning. With breast cancer, adjuvant therapy usually refers to medications given after surgery to treat any remaining cancer cells.

Effectiveness for treatment of metastatic breast cancer

In clinical trials, Kadcyla was an effective treatment for HER2+ metastatic breast cancer.

The National Comprehensive Cancer Network’s (NCCN) current treatment guidelines include Kadcyla as a treatment option for this type of breast cancer.

For details on how the drug performed in clinical trials for metastatic breast cancer, see the manufacturer’s site or Kadcyla’s prescribing information.

Kadcyla for adjuvant treatment of early breast cancer

Kadcyla is approved as an adjuvant therapy for HER2+ early breast cancer in certain people. Early breast cancer is cancer that hasn’t spread outside the breast tissue or surrounding lymph nodes.

Adjuvant therapy is a treatment that’s meant to prevent cancer from returning. With breast cancer, adjuvant therapy usually refers to medications given after surgery to treat any remaining cancer cells.

For this use, Kadcyla is prescribed to people who still have cancer cells remaining after neoadjuvant therapy* with certain drugs. These drugs include trastuzumab (Herceptin), and a taxane chemotherapy drug.

* Neoadjuvant therapy is a treatment that’s meant to shrink a tumor before undergoing surgery to remove it.

Effectiveness for adjuvant treatment of early breast cancer

In clinical trials, Kadcyla was an effective adjuvant treatment for HER2+ early breast cancer.

The NCCN’s current treatment guidelines include Kadcyla as a treatment option for this type of breast cancer.

For details on how the drug performed in clinical trials for early breast cancer, see the manufacturer’s site or Kadcyla’s prescribing information.

Kadcyla and children

Kadcyla is only FDA-approved to treat certain types of breast cancer in adults. The drug’s safety and effectiveness in children isn’t known.

The Kadcyla dosage your doctor prescribes will depend on several factors. These include:

  • your body weight
  • whether you develop any side effects* and how severe they are

The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs.

* For more information about side effects, see “Kadcyla side effects” above.

Drug forms and strengths

Kadcyla comes as powder inside single-dose vials. It’s mixed with liquid to form a solution. The solution is given as an IV infusion by a healthcare professional.

Kadcyla vials are available in two strengths: 100 milligrams (mg) and 160 mg.

Dosage for treatment of metastatic breast cancer

The recommended dose of Kadcyla for metastatic breast cancer is 3.6 mg per kilogram (mg/kg) of your body weight. (One kg is equal to about 2.2 pounds.)

You’ll receive one dose of Kadcyla every 3 weeks. You’ll continue this schedule for as long as your doctor recommends. How long you’ll take Kadcyla depends on whether it’s effective or if you develop severe side effects. (For more information, see “Kadcyla side effects” above.)

Dosage for adjuvant treatment of early breast cancer

The recommended dose of Kadcyla for early breast cancer is 3.6 mg/kg of your body weight.

You’ll receive one dose of Kadcyla every 3 weeks. Each 3-week period is called a “cycle.” You’ll likely continue this schedule for a total of 14 cycles, or as long as your doctor recommends. This depends on whether it’s effective or if you develop severe side effects.

What if I miss a dose?

If you miss a dose of Kadcyla, contact your doctor’s office right away. It’s important to reschedule your missed appointment as soon as possible. Your next dose will be rescheduled based on your new date. Your doctor will ensure that your Kadcyla doses are given only once every 3 weeks.

To help make sure that you don’t miss a dose, try using a medication reminder. This can include setting an alarm or using a timer. You could also download a reminder app on your phone.

Will I need to use this drug long term?

Kadcyla is meant to be used as a long-term treatment. How long you’ll take Kadcyla depends on whether it’s effective for your condition. It will also depend on whether you develop severe side effects.

There are no known interactions between Kadcyla and alcohol.

However, drinking alcohol, especially heavily, may cause liver problems. And Kadcyla can also cause serious liver damage.

In fact, Kadcyla has a boxed warning about the risk of this side effect. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous. For more information, see “Side effect details” in “Kadcyla side effects” above.

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

Kadcyla may interact with other medications.

Different interactions can cause different effects. For instance, some interactions can interfere with how well a drug works. Other interactions can increase side effects or make them more severe.

Kadcyla and other medications

Below is a list of medications that can interact with Kadcyla. This list does not contain all drugs that may interact with Kadcyla.

Before receiving Kadcyla, talk with your doctor and pharmacist. Tell them about all prescription, over-the-counter, and other drugs you take. Also tell them about any vitamins, herbs, and supplements you take. Sharing this information can help you avoid potential interactions.

Drugs that increase side effects of Kadcyla

Kadcyla may interact with certain drugs, which may increase your risk of side effects with Kadcyla. Examples of these drugs include:

Drugs that affect platelets

If you take certain medications that affect your platelets, your doctor may monitor you more carefully with Kadcyla treatment. (Platelets are blood cells that clot together to stop you from bleeding too much after an injury.) Taking these medications with Kadcyla may raise your risk of thrombocytopenia (low level of platelets) or serious bleeding. These types of medications include:

If you have questions about drug interactions that may affect you, ask your doctor or pharmacist.

Kadcyla and herbs and supplements

There aren’t any herbs or supplements that have been specifically reported to interact with Kadcyla. But you should still check with your doctor or pharmacist before taking any of these products while receiving Kadcyla treatment.

Kadcyla and foods

There aren’t any foods that have been specifically reported to interact with Kadcyla. If you have any questions about eating certain foods with Kadcyla, talk with your doctor.

Kadcyla comes as powder inside single-dose vials. It’s mixed with liquid to form a solution. The solution is given as an IV infusion.

When it’s given

Kadcyla will be given to you by a healthcare professional in a hospital or doctor’s office. You’ll likely receive one dose every 3 weeks. (For more information on dosage, see the “Kadcyla dosage” section above.)

The first infusion of Kadcyla will likely be 90 minutes long. If you don’t have severe infusion-related side effects, your next infusions will likely be 30 minutes long. If you have infusion-related side effects, your doctor may slow down, adjust, or stop the infusion. (For more information about infusion-related side effects, see “Side effect details” in “Kadcyla side effects” above.)

To help make sure that you don’t miss a dose, try using a medication reminder to notify you of your upcoming infusion appointments. This can include setting an alarm or using a timer. You could also download a reminder app on your phone.

Kadcyla is used to treat metastatic or early breast cancer that’s HER2-positive (HER2+) in certain adults. To learn more about metastatic and early breast cancer, see the “Kadcyla uses” section above.

Breast cancer occurs when cells in the breast start to multiply (make more cells) uncontrollably. When you’re diagnosed with breast cancer, your doctor will take a biopsy (tissue sample) of your breast tissue for testing. The results will provide information about the type of breast cancer you have. This, along with other factors, will help to determine the best treatment plan for you.

One of these tests may check for HER2. This is a protein involved in cell growth. Cancer cells that have high levels of HER2 are called HER2+. These cancer cells may grow and spread more quickly than typical cancer cells.

Kadcyla contains the active ingredient ado-trastuzumab emtansine. It’s an antibody-drug conjugate (two molecules that are chemically linked together). Ado-trastuzumab (the antibody component), belongs to a group of drugs called HER2-targeted therapies.

Ado-trastuzumab targets and attaches to HER2 receptors (binding sites) on the breast cancer cells. This signals your body’s immune system to destroy them. Also, this allows emtansine (the chemotherapy drug) to be released into the cell. Once inside the cell, the drug disrupts the cell’s growth process, leading to cell death.

Because of how Kadcyla is designed, it’s considered to be a targeted therapy for HER2+ cancer cells. (Targeted therapies only affect specific molecules in the body.)

To know if Kadcyla is right for your type of breast cancer, talk with your doctor.

How long does it take to work?

Kadcyla starts working as soon as you get your first dose or cycle of the drug. (Kadcyla is given once every 3 weeks and each 3-week period is called a “cycle.”)

During Kadcyla treatment, you may not notice any changes. And you may not be able to tell if any cancer tumors are shrinking.

Your doctor will order certain tests during your Kadcyla treatment to check how well the drug is working for you. They’ll also talk with you about how long you’ll continue Kadcyla.

You should not receive Kadcyla treatment if you’re pregnant or planning to become pregnant. Having Kadcyla treatment while pregnant may cause pregnancy loss. It could also cause harm in fetal development (commonly called “birth defects”).

In fact, Kadcyla has a boxed warning about the risk of this side effect. A boxed warning is the strongest warning required by the FDA. Boxed warnings alert doctors and patients about drug effects that may be dangerous.

If you’re able to become pregnant, your doctor will have you take a pregnancy test. This is to make sure that you’re not pregnant before starting Kadcyla treatment.

If you become pregnant while receiving Kadcyla treatment, or within 7 months after your last dose, tell your doctor right away. You’re also encouraged to report your pregnancy to a pregnancy registry. Pregnancy registries help medical professionals collect information about the safety of certain drugs. This information can help people make informed decisions about treatments during pregnancy.

You can learn more by talking with your doctor or calling the Kadcyla Pregnancy Exposure Registry at 888-835-2555.

Kadcyla and fertility

Based on animal studies, it’s possible that Kadcyla could affect your fertility (the biological ability to have children).

If you plan to conceive a child in the future, it’s important to talk with your doctor before starting Kadcyla. They’ll discuss your family planning options with you and help you weigh the risks and benefits of Kadcyla treatment.

Kadcyla treatment is not safe to have during pregnancy. If you’re sexually active and you or your partner can become pregnant, talk with your doctor about your birth control needs while you’re receiving Kadcyla treatment.

For more information about receiving Kadcyla treatment during pregnancy, see the “Kadcyla and pregnancy” section above.

For females using Kadcyla

If you’re female* who’s able to become pregnant, you should use birth control while receiving Kadcyla treatment. And you should continue using birth control for at least 7 months after your last dose of Kadcyla.

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

For males using Kadcyla

If you’re male* and your partner can become pregnant, you should use birth control while receiving Kadcyla treatment. You should continue using birth control for at least 4 months after your last dose of Kadcyla.

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

Kadcyla treatment is not safe to receive while breastfeeding. You should not breastfeed a child during treatment or for 7 months after your last dose of Kadcyla.

The drug hasn’t been specifically tested in people who are breastfeeding. But research in animals shows that trastuzumab, an ingredient in Kadcyla, passes into the breast milk of monkeys. And emtansine, another ingredient in Kadcyla, is thought to cause serious side effects in a breastfed child.

If you have questions about the best way to feed your child while receiving Kadcyla treatment, talk with your doctor.

This drug comes with several precautions.

FDA warnings

This drug has boxed warnings. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). It alerts doctors and patients about drug effects that may be dangerous.

Liver damage. While receiving Kadcyla, some people have developed severe liver damage, including liver failure. In some cases, liver failure may be life threatening. If you have symptoms of liver damage, tell your doctor or seek immediate medical care. These symptoms can include nausea, vomiting, pain in your right upper abdomen. You may also have dark-colored urine, loss of appetite, jaundice, and itchiness. (For more information, see the “Kadcyla side effects” section above.)

Serious heart problems. Kadcyla may cause changes in the amount of blood the heart can pump. Your doctor can check for this by measuring your left ventricular ejection fraction (LVEF) before and during your treatment. (The left ventricle is one of four chambers of the heart. Its job is to pump oxygenated blood to your body.) Your LVEF may decrease while you’re receiving Kadcyla. This can increase the risk of heart failure. Tell your doctor right away if you develop symptoms of this condition. They can include shortness of breath, cough, swelling of your legs or ankles, and heart palpitations. You may also have sudden weight gain (more than 5 pounds in 24 hours), dizziness, or fainting. (To learn more, see the “Kadcyla side effects” section above.)

Fetal harm. Kadcyla may cause pregnancy loss or harmful effects in a developing fetus. If you’re able to become pregnant, your doctor will have you take a pregnancy test before starting Kadcyla. If you or your partner can become pregnant, you should use birth control during treatment. Females* should continue using birth control for at least 7 months after their last dose of Kadcyla. Males* should continue using birth control for at least 4 months after their last dose of Kadcyla.

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

Other precautions

Before receiving Kadcyla treatment, talk with your doctor about your health history. Kadcyla may not be right for you if you have certain medical conditions or other factors affecting your health. These include:

  • Allergic reaction. If you’ve had an allergic reaction to Kadcyla or any of its ingredients, your doctor will likely not prescribe Kadcyla. Ask your doctor what other medications are better options for you.
  • Pregnancy. Kadcyla treatment is not safe to receive during pregnancy. For more information, see the “Kadcyla and pregnancy” section above.
  • Breastfeeding. Kadcyla treatment is not safe to have while breastfeeding. For more information, see the “Kadcyla and breastfeeding” section above.

Note: For more information about the potential negative effects of Kadcyla, see the “Kadcyla side effects” section above.

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.

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