Key takeaways

  • Zoladex, used to treat conditions like prostate cancer and endometriosis, can cause side effects ranging from mild issues like hot flashes and mood changes to more serious ones like heart problems and decreased bone density.
  • The side effects of Zoladex can vary depending on the condition it is used to treat. For instance, mood changes are more commonly reported in people treated for endometriosis or breast cancer compared to people treated for prostate cancer.
  • It’s important to discuss potential side effects and necessary monitoring with your doctor before starting Zoladex, especially if you have pre-existing conditions like heart problems, diabetes, or osteoporosis.

Zoladex is specifically used for:

  • prostate cancer that hasn’t spread to areas outside of the prostate
  • advanced prostate cancer, which is cancer that has spread from the prostate to other parts of the body
  • advanced breast cancer, which is cancer that has spread from the breast to other parts of the body
  • endometriosis, a condition in which tissue grows abnormally outside of the uterus
  • abnormal menstrual bleeding

For abnormal menstrual bleeding, Zoladex is used in the short term before endometrial ablation. This procedure removes the lining of the uterus. For Zoladex’s other uses, it is usually a long-term treatment.

Some people may experience mild or serious side effects during their Zoladex treatment. Examples of Zoladex’s commonly reported side effects include:

These are a few of the more common side effects reported by people taking Zoladex in studies of the 3.6-milligram (mg) implant and the 10.8-mg implant. These side effects can vary, depending on the condition the drug is treating.

More common side effects of Zoladex used for prostate cancer include:

  • hot flashes
  • ED
  • difficulty passing urine

More common side effects of Zoladex used for endometriosis, advanced breast cancer, or abnormal menstrual bleeding include:

For more information about some of these side effects, see the “Side effects explained” section.

Mild side effects of Zoladex can vary, depending on the condition the drug is treating.

Examples of mild side effects that have been reported with Zoladex for prostate cancer include:

Examples of some mild side effects that are possible with Zoladex treatment for endometriosis, breast cancer, or abnormal menstrual bleeding include:

In most cases, these side effects should be temporary. And some may be managed easily. But if you have any symptoms that are ongoing or that bother you, talk with your doctor. And don’t stop treatment with Zoladex unless your doctor recommends it.

For more information about some of these side effects, see the “Side effects explained” section. You can also see the Zoladex patient information for the 3.6-mg implant and the 10.8-mg implant for all side effects.

Note: The use of binary terms such as “male” and “female” or “men” and “women” in this article reflects the language of the sources we’ve used. Unless otherwise noted, it’s unclear whether the research we reference included participants with expansive gender identities.

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Less commonly, serious side effects have occurred in some people who used Zoladex. Serious side effects that have been reported with Zoladex include:

If you develop serious side effects while using Zoladex, 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.

For more information about some of these side effects, see the “Side effects explained” section.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone. It gives doctors and researchers more information about how the drug works in real life. If you develop a side effect while taking Zoladex and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

Like most drugs, Zoladex can cause an allergic reaction in some people.

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 difficult to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. To manage your symptoms, they may suggest an over-the-counter antihistamine that you take by mouth, such as Benadryl (diphenhydramine). They may also suggest a product that you apply to your skin, such as hydrocortisone cream.

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.

Your doctor can confirm whether you’ve had a mild or a serious allergic reaction to Zoladex. If it was mild, they can determine whether you should continue using the drug. If it was serious, they may switch you to a different treatment.

Learn answers to some frequently asked questions about the side effects of Zoladex.

Are any of Zoladex’s side effects long term?

Yes. Although they’re less common, Zoladex can cause long-term side effects.

In studies of the 3.6-mg implant and the 10.8-mg implant, Zoladex was shown to decrease bone mineral density (BMD) in some people. Low BMD can increase your risk of osteoporosis (thinning bones). Osteoporosis may, in turn, increase your risk of bone fracture, even after you stop using Zoladex.

Other side effects that may affect you long term include an increased risk of cardiovascular problems, such as heart attack and stroke.

To learn more about possible long-term side effects of Zoladex, talk with your doctor.

Will I have fewer side effects with the 3.6-mg implant than the 10.8-mg implant? Are the side effects different between these doses?

It’s unlikely. Both strengths of Zoladex seem to cause similar side effects.

A study compared the safety and effectiveness of the drug for advanced breast cancer in females who hadn’t gone through menopause. The results showed that the effects of the drug were the same, whether it was given as a 3.6-mg implant monthly or as a 10.8-mg implant every 3 months.

If you have questions about side effects due to Zoladex dosage, talk with your doctor.

Will I have side effects if I stop my Zoladex treatment?

It’s possible. Zoladex is an implant that a healthcare professional inserts under your skin according to your prescribed implant schedule. It’s designed to dissolve over time.

If you develop a rare but serious allergic reaction or side effect, your doctor will likely remove the implant. Removal of the implant may cause temporary pain around the implant site. Your doctor may let the Zoladex implant dissolve on its own if your reaction isn’t severe. It dissolves around 4 weeks after insertion, but its effects last up to 12 weeks in your body. During this time, you may notice changes as your hormone production increases to your natural level.

When stopping (or “coming off”) Zoladex, the resulting effects can vary, depending on the condition Zoladex was treating. For example:

  • People with prostate cancer who stop Zoladex may notice their symptoms worsening.
  • Females who haven’t gone through menopause and stop Zoladex may have their period return within 12 weeks. (It’s likely that your period will stop during Zoladex treatment.)

If you have questions about ending your treatment with Zoladex, talk with your doctor.

Do Zoladex’s side effects vary, depending on the condition it’s used to treat (prostate cancer, endometriosis, or breast cancer)?

Yes, some of the common side effects of Zoladex vary, depending on the condition being treated.

For example, mood changes and depression are more common side effects in people having the treatment for endometriosis or breast cancer. Mood-related side effects weren’t commonly reported in studies of the 3.6-mg implant and the 10.8-mg implant for prostate cancer.

For more information, see the “What are the more common side effects of Zoladex?” section. If you have questions about the side effects that Zoladex can cause for people with your condition, talk with your doctor.

How soon do side effects of Zoladex start?

Zoladex releases goserelin, its active drug, very slowly for the first 8 days after it’s implanted under your skin. During this first week, you may notice injection site injury, such as pain or bruising, where Zoladex was inserted.

For some people with breast cancer or prostate cancer, Zoladex can cause a short-term increase in tumor growth. This may happen when they first start using the drug. Worsening of cancer symptoms, such as bone pain, may occur during the first few weeks after Zoladex is implanted.

Zoladex works to lower the amount of sex hormone (testosterone or estrogen) in your body. After your first Zoladex implant, it takes 2 to 4 weeks for your hormone levels to drop.

Many of Zoladex’s side effects, such as hot flashes, acne, and sexual problems, are related to this drop in hormone level. As a result, you may notice most of Zoladex’s side effects starting within 2 to 4 weeks.

Learn more about some side effects that Zoladex may cause.

Depression

Depression was reported as a common side effect of Zoladex. Specifically, it was reported in studies of the 3.6-mg implant and the 10.8-mg implant for treating breast cancer, endometriosis, and abnormal menstrual bleeding.

Symptoms of depression may last for 2 weeks or longer and often include:

  • feelings of sadness or hopelessness
  • loss of interest in your favorite activities
  • lack of energy or motivation
  • difficulty concentrating
  • changes in your usual appetite or sleep patterns

What might help

If you or your loved ones notice that you have symptoms of depression, talk with your doctor. They may suggest one or more treatment options that can help ease depression, such as:

  • antidepressant medications
  • talk therapy with a licensed counselor or psychologist
  • in-person or online support groups for people with your condition
  • regular physical exercise, as recommended by your doctor

Injection site injury

Injection site injury is a less common but possible side effect of Zoladex. Because Zoladex is an implant, you may develop reactions at the spot where it’s placed under your skin.

Skin-related injection site symptoms may include:

  • pain or irritation at the insertion site
  • bruising of the skin or blood collecting under your skin
  • severe bleeding

It’s possible to develop serious symptoms after receiving a Zoladex implant. You should call your doctor right away if you have any of the following side effects:

You may have an increased risk of these side effects if you have a low body mass index or if you’re taking blood-thinning medications. Your doctor will monitor you carefully during and after your Zoladex implant is inserted.

What might help

Skin-related injection site injury is temporary and usually goes away on its own. To ease pain at the implant site, you might take an over-the-counter pain reliever, such as acetaminophen (Tylenol).

You could also ask whether you can have an ice pack applied to the insertion area beforehand. In an old study from 2013, applying an ice pack for a short period significantly reduced the pain of a Zoladex injection.

If you have concerns about injection site injury with Zoladex, talk with your doctor.

Weight gain

In studies of the 3.6-mg implant and the 10.8-mg implant, weight gain was reported as a side effect of Zoladex, but it wasn’t common.

Increased appetite and fluid retention have also been reported in people receiving Zoladex treatment. It isn’t known whether these side effects are related to weight gain caused by using the drug.

What might help

If you have weight gain during Zoladex treatment, talk with your doctor. They may be able to help you identify contributing factors. They may also recommend ways to maintain a healthy weight, such as changing your diet or exercise routines.

Keeping track of side effects

During your Zoladex treatment, consider keeping notes about any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful 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 received when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Zoladex affects you. Your doctor can use this information to adjust your treatment plan if needed.

Zoladex 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 you receive Zoladex. The list below includes some factors to consider.

Heart problems: Although it isn’t common, Zoladex can cause abnormal heart rhythms, heart attack, or stroke. If you already have heart disease, Zoladex treatment can further increase these risks. Before starting Zoladex, talk with your doctor about your past or current heart problems. They may suggest a different treatment option for you.

Diabetes: Zoladex can cause high blood sugar levels. If you have diabetes, Zoladex may make it harder to manage your blood sugar. As a result, your doctor may suggest changes to your diabetes treatment plan or blood sugar monitoring.

Bone problems: If you have osteoporosis (thinning bones), Zoladex treatment can possibly worsen your condition. Because of this, your doctor may use X-rays or bone scans to monitor your bone mineral density.

Allergic reaction: You shouldn’t use Zoladex if you’ve ever had an allergic reaction to it or any of its ingredients. You also shouldn’t use Zoladex if you’ve had an allergic reaction to a drug that’s similar to it. Before starting Zoladex treatment, be sure to tell your doctor about any allergic reactions you’ve had in the past. They can tell you about other medications that may be better options for you.

Alcohol use and Zoladex

For most people, occasional or moderate alcohol use is safe during Zoladex treatment.

But long-term alcohol use can increase the risk of bone loss. Zoladex treatment may increase this risk, especially in people who already have osteoporosis.

If you drink alcohol, talk with your doctor about how much is safe for you to consume while using Zoladex.

Pregnancy while using Zoladex

It’s unsafe to use Zoladex during pregnancy. The manufacturer notes that Zoladex should not be used in someone who is pregnant except during palliative treatment of advanced breast cancer. (Palliative treatment eases symptoms of a disease but doesn’t cure the disease itself.) Zoladex may cause harmful effects to a fetus or increase the risk of pregnancy loss.

If you can become pregnant, talk with your doctor about birth control options during your Zoladex treatment. It’s recommended that you use nonhormonal birth control during Zoladex treatment and for 12 weeks after the treatment ends.

If you’re pregnant or planning a pregnancy, talk with your doctor before starting Zoladex. They’ll recommend the best treatment plan for you during this time.

Breastfeeding while using Zoladex

It’s recommended that you not use Zoladex while breastfeeding. This is because the effects of Zoladex on a breastfed child aren’t known. The manufacturer notes that Zoladex should not be used in someone who is breastfeeding except during palliative treatment of advanced breast cancer. (Palliative treatment eases symptoms of a disease but doesn’t cure the disease itself.)

If you’re breastfeeding or planning to, talk with your doctor before starting Zoladex. They can discuss options with you for this time.

Q:

How can I prevent or reduce the sexual side effects caused by Zoladex?

Anonymous

A:

Sexual side effects are common in people who are using Zoladex.

Depending on the specific side effect, your doctor may recommend certain treatments or lifestyle changes. These can include:

  • prescription or over-the-counter medications and supplements
  • changes to your diet
  • pelvic floor exercises, such as Kegel exercises
  • sex therapy
  • sex aids

Talk with your doctor if you have questions about how to manage sexual side effects while using Zoladex.

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.