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Firmagon

Pronunciation: FIRM-uh-gahn
Generic name: degarelix
Dosage form: injection for subcutaneous use (80 mg, 120 mg)
Drug classes: Gonadotropin-releasing hormone antagonists, Hormones / antineoplastics

Medically reviewed by Carmen Pope, BPharm. Last updated on May 22, 2025.

What is Firmagon?

Firmagon injection is used to treat advanced prostate cancer. It works by decreasing the amount of testosterone in the body, which the tumor needs to grow. It is given by subcutaneous (under the skin) injection once every 28 days by a healthcare provider.

Firmagon is a man-made form of a protein that works by blocking specific hormone receptors in your brain's pituitary gland called GnRH receptors. This immediately stops the chain reaction that leads to testosterone production. Since prostate cancer cells need testosterone to grow, reducing this hormone helps control the cancer's spread and growth. Firmagon belongs to the drug class called GnRH receptor antagonists.

Fimragon gained FDA approval on December 24, 2008. There is no generic.

Firmagon side effects

The most common side effects of Firmagon are:

Fimragon may also affect your sex drive and cause erectile function problems.

Serious side effects and warnings

Firmagon can cause the following serious side effects:

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.

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

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.

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 the  FDA at 1-800-FDA-1088.

Before taking this medicine

You should not use Firmagon if you are allergic to degarelix, Firmagon, or any of the inactive ingredients in the injection.

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

Firmagon is only for use by men.

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

How is Firmagon administered?

A healthcare provider will give you this injection.

The first time you receive this medicine, you will be given two injections.

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 medicine.

Dosing information

Usual Adult Dose of Firmagon for Prostate Cancer:

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

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.

Firmagon 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.

What other drugs will affect this medicine?

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.

Does Firmagon interact with my other drugs?

Enter medications to view a detailed interaction report using our Drug Interaction Checker.

Ingredients

Active ingredient: degarelix (as acetate)
Inactive ingredient: mannitol.

Who makes Firmagon?

Firmagon is made by Ferring Pharmaceuticals in Germany. Ferring Pharmaceuticals also has headquarters in Parsippany, NJ. 

Popular FAQ

How does Firmagon work for prostate cancer?

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.

How long does Firmagon stay in your system?

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.

How long can I use Firmagon injections?

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.

How long do Firmagon side effects last?

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.

Is Firmagon (degarelix) the same as Lupron?

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
How long does it take for Degarelix to work?

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

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