Zoladex (goserelin) is a prescription drug used to treat certain types of cancer, manage endometriosis, and more. The drug comes as an implant that’s inserted under your skin. This is typically done once every 28 days.
Zoladex is used in adults to:
- treat prostate cancer that hasn’t spread to other areas of your body*
- provide palliative care if you have prostate cancer or breast cancer that’s spread to other areas of your body
- treat endometriosis
- thin the lining of your uterus (endometrium) before an endometrial ablation if you experience bleeding apart from your normal menstrual cycle
The active ingredient in Zoladex is goserelin. (An active ingredient is what makes a drug work.) Zoladex belongs to a group of drugs called gonadotropin-releasing hormone (GnRH) agonists.
This article describes the dosages of Zoladex, as well as its strengths and how it’s given. To learn more about Zoladex, see this in-depth article.
* For this use, Zoladex is used together with the drug flutamide.
The table below highlights the basics of Zoladex’s dosage. All doses are listed in milligrams (mg).
| Use | Typical dosage |
|---|---|
| prostate cancer that hasn’t spread to other areas of your body* | 3.6-mg implant inserted 8 weeks before radiation begins, then 10.8-mg implant inserted* 28 days later |
| palliative care of prostate cancer that’s spread to other areas of your body | 3.6-mg implant inserted every 28 days or 10.8-mg implant inserted every 12 weeks |
| palliative care of breast cancer that’s spread to other areas of your body | 3.6-mg implant inserted every 28 days |
| endometriosis | 3.6-mg implant inserted every 28 days for 6 months |
| before endometrial ablation for abnormal uterine bleeding | one or two 3.6-mg implants inserted 4 weeks apart |
* For this use, Zoladex is used together with the drug flutamide.
Keep reading for more details about Zoladex’s dosage.
What is Zoladex’s form?
Zoladex comes as an implant that’s inserted under your skin by a healthcare professional.
What strengths does Zoladex come in?
Zoladex comes in two strengths: 3.6 mg and 10.8 mg.
What are the usual dosages of Zoladex?
The information below describes dosages that are commonly used or recommended. But your doctor will determine the best dosage to meet your needs.
Dosage for prostate cancer
The typical Zoladex dosage for adults with prostate cancer that hasn’t spread to other areas of the body is 3.6 mg inserted 8 weeks before you begin radiation therapy. Then, 28 days later, you’ll receive another dose of 10.8 mg.
Alternatively, you can receive four 3.6-mg doses — one every 28 days. This may mean that you’ll receive two 3.6-mg doses before radiation starts. You may then receive another two 3.6-mg doses during radiation therapy.
You’ll take flutamide with Zoladex, and you’ll continue Zoladex treatment while you receive radiation.
Dosage for palliative care of advanced prostate cancer
The typical Zoladex dosage for palliative care for adults with prostate cancer that’s spread to other areas of the body is 3.6 mg every 28 days. Or your doctor may prescribe 10.8 mg every 12 weeks.
Dosage for endometriosis
The typical Zoladex dosage for adults (18 years and older) with endometriosis is 3.6 mg every 28 days. You’ll receive Zoladex for 6 months. Based on studies, the effects of Zoladex treatment lasting longer than 6 months for endometriosis are not yet known.
Dosage for palliative care of breast cancer
The typical dosage of Zoladex for palliative care for adults with breast cancer that’s spread to other areas of the body is 3.6 mg every 28 days.
Dosage for abnormal uterine bleeding
The typical dosage of Zoladex for adults preparing for endometrial ablation is one or two 3.6-mg implants inserted 4 weeks apart. Your doctor may recommend an endometrial ablation if you have bleeding apart from normal menstruation.
If your doctor recommends you receive one dose, you’ll likely have the endometrial ablation 4 weeks later.
If your doctor recommends you receive two doses, you’ll likely have the endometrial ablation within 2–4 weeks of receiving your second dose.
Is Zoladex used long term?
Yes, Zoladex is usually used as a long-term treatment for management of prostate or breast cancer. If you and your doctor determine that it’s safe and effective for your condition, you’ll likely use it long term.
The dosage of Zoladex you’re prescribed may depend on several factors. These include:
- the type and severity of the condition you’re using the drug to treat
- your age
- other conditions you may have
Zoladex comes inside a solid implant, which is about 1 centimeter long for the 3.6-milligram (mg) strength. A healthcare professional uses a syringe to insert the implant under your skin in a doctor’s office or clinic.
Your doctor will have you lie on your back with your upper body slightly elevated. They’ll clean an area near your belly button with alcohol. Then they’ll pinch this skin together and insert the syringe needle at an angle to inject the dose.
If you miss an appointment to receive a dose of Zoladex, call your doctor’s office as soon as possible to reschedule. Studies say that missing your dose by a few days is allowable, but you should make every effort to keep your appointments as scheduled. If you need help remembering your appointments, try downloading a reminder app on your phone.
Below are answers to some commonly asked questions about Zoladex’s dosage.
Is the dosage of Zoladex similar to that of Lupron Depot or tamoxifen?
Zoladex and Lupron Depot (leuprolide acetate) are similar in how they’re given, but the frequency may differ.
Both drugs are injections given by a doctor, but Zoladex is injected under your skin, while Lupron Depot is injected into a muscle. Zoladex is given once every 28 days or 12 weeks, while Lupron Depot may be given once every 4, 12, 16, or 24 weeks.
Tamoxifen comes as a liquid solution or tablet that you swallow and is usually taken daily.
The dose in milligrams for each drug also differs. Your doctor will prescribe the drug and dosage that’s right for you. Talk with them to learn more about how these drugs compare.
How long does Zoladex take to start working?
Zoladex starts to work after your first dose. At first, you may experience higher levels of testosterone if you have prostate cancer. Or you may have higher levels of estrogen if you have breast cancer. These higher levels may temporarily cause your symptoms, such as cancer-related pain, to worsen. This is called tumor flare phenomenon.
After a few weeks, your levels of estrogen or testosterone will likely fall. These lowering levels mean the drug is starting to exert its full beneficial effect. But your doctor will monitor you during treatment to check whether the drug is working to treat your condition.
If you have other questions about what to expect from your Zoladex treatment, talk with your doctor.
The sections above describe the usual dosages provided by the manufacturer. If your doctor recommends Zoladex for you, they’ll prescribe the dosage that’s right for you.
Talk with your doctor if you have questions or concerns about your current dosage. Here are some examples of questions you may want to ask:
- How will my dosage of Zoladex be decided if I have prostate cancer?
- Can I repeat courses of Zoladex as needed for endometriosis management?
- Will using Zoladex for a shorter time (such as for preparing for endometrial ablation) lower my risk of side effects?
To learn more about Zoladex, 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.
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.