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Generic name: degarelixDEG-a-REL-ix ]
Drug classes: Gonadotropin-releasing hormone antagonists, Hormones / antineoplastics

Medically reviewed by Philip Thornton, DipPharm. Last updated on Aug 23, 2023.

What is Firmagon?

Firmagon is a man-made form of a protein that reduces the amount of certain hormones in the body, including testosterone.

Firmagon injection is used to treat prostate cancer. It works by decreasing the amount of testosterone in the body, which the tumor needs to grow.

It is not known if Firmagon is safe or effective in children.


Although Firmagon is not for use by women, degarelix should not be used by a woman who is pregnant or breast-feeding, or who may become pregnant.

Before you receive Firmagon, tell your doctor if you have liver or kidney disease, a personal or family history of "Long QT syndrome," congestive heart failure, or an electrolyte imbalance, such as low or high levels of potassium or magnesium in your blood.

Tell your doctor about all other medications you use, especially a heart rhythm medication.

Firmagon is usually given once every 28 days. Follow your doctor's instructions.

To be sure this medication is helping your condition, your blood may need to be tested on a regular basis. Do not miss any follow-up visits to your doctor.

Before taking this medicine

You should not use Firmagon if you are allergic to degarelix.

To make sure Firmagon is safe for you, tell your doctor if you have:

Although Firmagon is not for use by women, degarelix can harm an unborn baby or cause miscarriage if a woman is exposed to it during pregnancy. Degarelix should not be used by a woman who is pregnant.

This medicine may affect fertility (your ability to have children), whether you are a man or a woman.

Firmagon also should not be used by a woman who is breastfeeding a baby.

How is Firmagon given?

Firmagon is injected under the skin around your stomach. A healthcare provider will give you this injection.

On the day of your injection, avoid wearing a belt, tight waistband, or tight clothing around your stomach where the injection will be given.

Firmagon is usually given once every 28 days. Follow your doctor's instructions.

The first time you receive this medicine, you will be given two injections. At your monthly follow-up visits you will receive only one injection.

You will need frequent medical tests.

Firmagon can affect the results of certain medical tests. Tell any doctor who treats you that you are using this degarelix.

Dosing information

Usual Adult Dose for Prostate Cancer:

-Initial Dose: 240 mg administered as 2 subcutaneous injections of 120 mg each at a concentration of 40 mg/mL.

-Maintenance Dose: 80 mg administered as 1 subcutaneous injection at a concentration of 20 mg/mL every 28 days.

Comments: Administer the first maintenance dose 28 days after the initial dose.

Use: Treatment of advanced prostate cancer

What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your Firmagon injection.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while receiving Firmagon?

Avoid rubbing or scratching the skin where the injection was given.

Degarelix can pass into body fluids (urine, feces, vomit). For at least 48 hours after you receive a dose, avoid allowing your body fluids to come into contact with your hands or other surfaces. Caregivers should wear rubber gloves while cleaning up a patient's body fluids, handling contaminated trash or laundry or changing diapers. Wash hands before and after removing gloves. Wash soiled clothing and linens separately from other laundry.

Firmagon side effects

Get emergency medical help if you have signs of an allergic reaction to Firmagon: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

Common Firmagon side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Firmagon?

Firmagon can cause a serious heart problem. Your risk may be higher if you also use certain other medicines for infections, asthma, heart problems, high blood pressure, depression, mental illness, cancer, malaria, or HIV.

Other drugs may interact with degarelix, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Popular FAQ

Firmagon works by binding to gonadotropin-releasing hormone (GnRH) receptors located in our pituitary gland (this is the small, bean-shaped gland situated at the base of our brains that produces hormones that control many of our bodily functions such as metabolism, growth, sexual maturation, and reproduction). By binding to GnRH receptors, Firmagon reduces the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and subsequently testosterone. Testosterone is an androgen hormone that can stimulate the growth of prostate cancer. Firmagon works almost immediately, with an initial injection causing a drop in testosterone levels of 88% after 1 day. Within 3 days, levels had dropped by 94%, and by 28 days, 98%. When given every 28 days, levels of testosterone remain at least 98% below normal.

Firmagon belongs to the class of medicines known as gonadotropin-releasing hormone (GnRH) receptor antagonists.

When Firmagon is injected under the skin of your abdomen, it forms a depot from which the drug is released in two phases into your blood stream – a short initial fast-release phase followed by a second slow-release phase – meaning that one dose of Firmagon stays in your system for many months. The half-life of Firmagon is 53 days, and experts calculate it takes 4 to 5 half-lives for a medicine to be completely removed from your body, which means that theoretically Firmagon lasts in your body for up to 265 days (nearly 9 months). Despite this long half-life, Firmagon still needs to be injected every 28 days to keep plasma levels of Firmagon high, constant, and above the threshold needed to keep testosterone levels low.

Firmagon is intended as a long-term treatment, and you will stay on it as long as you are tolerating it well and your prostate cancer has not progressed to the extent that treatment with Firmagon is not warranted anymore. Firmagon has been shown to be effective and well-tolerated in trials that followed people for an average of 43 months (range 1 to 58 months) or 3.5 years.

Injection site reactions, such as pain, redness, or swelling at the injection site, are the most common side effect reported in people administered Firmagon, occurring in 35% of people, but these are usually experienced after the first dose (only 4% reported injection site reactions with subsequent smaller maintenance doses), are mild-to-moderate, and get better within about 3 days. Other common side effects of Firmagon and their duration include:

  • Hot flashes – for many these will improve within a few months but for some, they will last for the duration of treatment
  • Liver enzyme elevations – these occur in one-third of people but are generally mild and resolve by themselves without dosage adjustment
  • Weight increase – this may persist for the duration of treatment unless measures are taken, such as dietary restriction and increased exercise, to limit weight gain
  • An increase in blood pressure or arrhythmias – your doctor should monitor your heart during treatment to check for any changes and treatment with Firmagon may need to be modified if these persist
  • Constipation – for many this may improve within a few weeks of taking Firmagon but laxatives should be taken initially to resolve any constipation
  • Back or joint pain – for many this improves within a few weeks of taking Firmagon but talk to your doctor about pain relief if it persists or is troublesome
  • A decrease in sex drive and erectile dysfunction – this usually persists for the duration of Firmagon treatment but talk to your doctor about other treatments that may help with this.

Other side effects of Firmagon were uncommon and generally mild to moderate.

No, Firmagon (degarelix) is not the same as Lupron but they are both hormone deprivation treatments that may be used for the treatment of advanced prostate cancer. Firmagon takes a more direct path to testosterone suppression than Lupron. Firmagon is an antagonist that immediately stops testosterone production, preventing a testosterone surge and eliminating the need for any additional therapies. Lupron is an agonist that desensitizes the GnRH receptor but causes an initial surge in testosterone and may require additional medication. Continue reading

Degarelix works almost immediately, with an initial injection of degarelix causing a drop in testosterone levels of 88% after 1 day. Within 3 days, levels had dropped by 94%, and by 28 days, 98%. When given every 28 days, levels of testosterone remain at least 98% below normal. Continue reading

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Firmagon only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.