Eligard is a brand-name injectable drug prescribed to help manage symptoms of advanced prostate cancer in adults. As with other drugs, Eligard can cause side effects, such as fatigue, hot flashes, and tumor flares.

Eligard 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 after each Eligard injection.* However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor.

These are just a few of the more common side effects reported by adult males† who received Eligard in clinical trials:

* Eligard is given by a doctor or other healthcare professional as a subcutaneous injection.
† Sex and gender exist on spectrums. Use of the term “male” in this article refers to sex assigned at birth.

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

Mild side effects that have been reported with Eligard include:

These side effects may be temporary, lasting a few days to weeks after each Eligard dose. (Eligard is given as a subcutaneous injection.) However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor.

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

* For more information about this side effect, see “Side effect specifics” below.
† An allergic reaction is possible after using Eligard. However, it’s not clear whether this side effect occurred in clinical trials. To learn more, see the “Side effect specifics” section below.

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

If you develop serious side effects during Eligard treatment, 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:

* There have been rare reports of this side effect since Eligard and similar drugs were approved for use. Your doctor can provide more information about your risk of these side effects with Eligard.
† For more information about this side effect, see “Side effect specifics” below.
‡ An allergic reaction is possible after using Eligard. However, it’s not clear whether this side effect occurred in clinical trials. To learn more, see the “Side effect specifics” section below.

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

Will side effects of Eligard go away?

Possibly. Some of the drug’s side effects may be temporary and go away within a few weeks after each Eligard dose. Examples include dizziness and nausea.

However, because of the way Eligard works, certain side effects may persist as long as you receive the drug. These include erectile dysfunction (ED) and testicular atrophy (decreased testicle size).* (To learn more about the way Eligard works, see the “How it works” section of this article.)

If the side effects don’t go away, bother you, or become severe, be sure to talk with your doctor.

* ED and testicular atrophy are serious side effects of Eligard. For more information, see the “Serious side effects of Eligard” section above.

When do side effects of Eligard start? And how long do they last?

Side effects of Eligard can start at any time during treatment. Some side effects go away within a few weeks, but they may last longer. (To learn more, see the question “Can Eligard cause long-term side effects?” below.)

For example, tumor flares* may occur with Eligard treatment. A tumor flare refers to an increase in prostate cancer symptoms due to a rise in testosterone levels. In Eligard’s clinical trials, tumor flares started about week 2 of treatment and began subsiding about week 4.†

It’s also possible for side effects to start after Eligard treatment ends. This is because the drug stays in your body for up to a year after your last dose.

If you have questions about what to expect with Eligard treatment, talk with your doctor for more information.

* This is a serious side effect of Eligard. To learn more, see the “Side effect specifics” section below.
† For more information about Eligard’s dosing schedule, see the “Dosage” section of this article.

Can Eligard cause long-term side effects?

Yes, on rare occasions, Eligard can cause long-term side effects. These side effects may occur during treatment but cause problems that persist after treatment ends. Examples of possible long-term side effects with Eligard include:

For more information about Eligard and its long-term side effects, talk with your doctor.

Note: Possible long-term side effects listed above are all serious side effects of Eligard. For details, see the “Serious side effects of Eligard” section above.

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

Weight gain

Eligard treatment may cause weight gain, but this side effect wasn’t common in the drug’s clinical trials.

Eligard works by lowering the level of testosterone in your body. This is a hormone that helps prostate cancer grow. Having low testosterone may lead to an increase in body fat, which could result in weight gain. The amount of weight gain can vary between people depending on the Eligard dose and other factors.

What you can do

You and your doctor will monitor your weight during Eligard treatment. Your doctor may also recommend a body weight that’s safe and healthy for you during Eligard treatment.

Tell your doctor if you notice unexpected weight gain while receiving Eligard. Your doctor will help determine the cause.

In some cases, your doctor may suggest some safe ways to lose or maintain your weight, such as proper nutrition and exercise. For more information about weight management, talk with your doctor.

Tumor flares

Some people who received Eligard in clinical trials experienced a tumor flare. With this side effect, prostate cancer cells grow and symptoms may worsen. A tumor flare may begin within 1–2 weeks of starting Eligard.

Eligard can cause a tumor flare because of how the drug works to help manage symptoms of advanced prostate cancer.

Eligard treatment lowers the level of testosterone, a hormone that helps prostate cancer grow. By lowering testosterone levels, Eligard slows cancer growth and helps relieve cancer symptoms. However, before testosterone levels decrease with Eligard, they initially increase. This temporary rise in testosterone triggers a tumor flare.

A tumor flare may lead to severe effects in certain people. This includes people with a blockage in their urinary tract or whose prostate cancer has spread to the spine.

Symptoms of a tumor flare vary depending on where in your body prostate cancer has spread. Tumor flare symptoms can include:

What you can do

Depending on your condition, your doctor may monitor you more closely when you first start Eligard. If you experience new or worsened symptoms, talk with your doctor right away. They’ll determine whether additional treatment is needed to ease your symptoms. Or, they may suggest a different medication for your condition.

Keep in mind that most people receiving Eligard in clinical trials did not experience a tumor flare. In addition, tumor flares are usually temporary events. Typically, symptoms start to decrease within 2–4 weeks after starting Eligard.

Talk with your doctor if you’d like more information about tumor flares.

Allergic reaction

As with most drugs, Eligard can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in clinical trials.

Symptoms can be mild or serious and can include:

  • skin rash
  • itching
  • flushing
  • 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 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 continue with Eligard treatment. However, if your symptoms are serious and you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Be sure to talk with your doctor about your health history before you start Eligard. This drug may not be the right treatment option for you if you have certain medical conditions or other factors that affect your health. These are considered drug-condition or drug-factor interactions. The conditions and factors to consider include:

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

Alcohol consumption: If you drink alcohol, Eligard is likely safe for you. This medication is not known to cause any specific negative effects with alcohol. However, both alcohol and Eligard may cause dizziness and fatigue as side effects. So consuming alcohol during Eligard treatment may worsen the medication’s effects.

If you drink alcohol and have questions about how much alcohol is safe to use when taking Eligard, talk with your doctor or pharmacist.

Diabetes: If you have diabetes, tell your doctor before starting Eligard treatment. This drug may cause high blood sugar,* which could worsen diabetes. Your doctor may monitor your blood sugar closely during Eligard treatment.

Cardiovascular conditions or related factors: Before starting Eligard treatment, tell your doctor if you have heart disease or factors that increase your risk of heart disease. Examples include high cholesterol and diabetes. Also tell them if you have any heart conditions, such as heart failure or long QT syndrome.

In addition, Eligard may cause irregular heart rhythm or other cardiovascular events,* including heart attack and stroke. The risk may be higher in people with any of the factors listed above. Your doctor can recommend whether Eligard is a safe treatment option.

Seizures: If you have a condition that causes seizures,* talk with your doctor before starting Eligard treatment. This drug may cause seizures as a side effect. Your risk could be higher if you already have a seizure condition. Your doctor can tell you whether Eligard is a safe treatment option.

Pregnancy or breastfeeding: If you’re pregnant or breastfeeding, Eligard may not be safe for your pregnancy or your child. Eligard has not been studied in people who are pregnant or breastfeeding. However, the drug may increase the risk of pregnancy loss. Note that this medication is not approved for use in females.† Eligard is approved to treat advanced prostate cancer in adult males.

* This is a serious side effect of Eligard. To learn more, see the “Serious side effects of Eligard” section above.
† Sex and gender exist on spectrums. Use of the terms “male” and “female” in this article refers to sex assigned at birth.

If you’d like to learn more about Eligard, 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.