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Generic name: degarelix
Drug classes: Gonadotropin-releasing hormone antagonists, Hormones / antineoplastics

Medically reviewed by  A Ras MD.

What is Firmagon used for?

Firmagon is used to treat prostate cancer. Firmagon may be given to you for other reasons.


FIRMAGON is a sterile lyophilized powder for injection containing degarelix (as the acetate) and mannitol. Degarelix is a synthetic linear decapeptide amide containing seven unnatural amino acids, five of which are D-amino acids. The acetate salt of degarelix is a white to off-white amorphous powder of low density as obtained after lyophilization.

The chemical name of degarelix is D-Alaninamide, N-acetyl-3-(2-naphthalenyl)-D-alanyl-4-chloro-D-phenylalanyl-3-(3-pyridinyl)-D-alanyl-L-seryl-4-[[[(4S)-hexahydro-2,6-dioxo-4-pyrimidinyl]carbonyl]amino]-L phenylalanyl-4-[(aminocarbonyl)amino]-D-phenylalanyl-L-leucyl-N6–(1-methylethyl)-L-lysyl-L-prolyl. It has an empirical formula of C82H103N18O16Cl and a molecular weight of 1632.3 Da.

Degarelix acetate has the following structural formula:

Chemical Structure

FIRMAGON is available in two packaging configurations:

  • Starting Dose: Two vial carton with each vial delivering 120 mg of degarelix (equivalent to the median value of 126 mg degarelix acetate). Each 120 mg dose contains 150 mg mannitol.
  • Maintenance Dose: One-vial carton delivering 80 mg of degarelix (equivalent to the median value of 84 mg degarelix acetate). Each 80 mg dose contains 200 mg mannitol.
  • Mechanism of Action

    Degarelix is a GnRH receptor antagonist. It binds reversibly to the pituitary GnRH receptors, thereby reducing the release of gonadotropins and consequently testosterone.

Before taking Firmagon, tell your doctor:

  • If you are allergic to Firmagon; any part of this medicine; or any other drugs, foods, or substances. Tell your doctor about the allergy and what signs you had.
  • If you have electrolyte (like sodium, potassium, phosphate) problems.
  • If you are a woman. This medicine is not approved for use in women. This medicine may cause harm to an unborn baby or loss of an unborn baby if it is taken during pregnancy. If you are a woman using Firmagon, talk with your doctor if you are pregnant, plan on getting pregnant, or are breast-feeding.

This is not a list of all drugs or health problems that interact with this medicine.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take Firmagon with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take Firmagon?

  • Tell all of your health care providers that you take Firmagon. This includes your doctors, nurses, pharmacists, and dentists.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • This medicine may cause weak bones. This may happen more often if used for a long time. This may raise the chance of broken bones. Call your doctor right away if you have bone pain.
  • Have a bone density test as you have been told by your doctor. Talk with your doctor.
  • You may need to have an ECG checked before starting Firmagon and while taking it. Talk with your doctor.
  • This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take Firmagon.
  • Do not scratch or rub the skin where Firmagon is given.

How is Firmagon best taken?

Use Firmagon as ordered by your doctor. Read all information given to you. Follow all instructions closely.

  • It is given as a shot into the fatty part of the skin.
  • Your doctor will give Firmagon.
  • Do not use pressure (waist band or belt) on the part where the shot is given.

What do I do if I miss a dose?

  • Call your doctor to find out what to do.

What are the side effects of Firmagon that I need to call my doctor about immediately?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
  • Signs of a urinary tract infection (UTI) like blood in the urine, burning or pain when passing urine, feeling the need to pass urine often or right away, fever, lower stomach pain, or pelvic pain.
  • A type of abnormal heartbeat (prolonged QT interval) can happen with Firmagon. Call your doctor right away if you have a fast heartbeat, a heartbeat that does not feel normal, or if you pass out.

What are some other side effects of Firmagon?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:

  • Weight gain.
  • Not able to get or keep an erection.
  • Lowered interest in sex.
  • Feeling tired or weak.
  • Hot flashes.
  • Back pain.
  • Joint pain.
  • Chills.
  • Constipation.
  • Redness or swelling where the shot is given.
  • Itching where the shot is given.
  • Pain where the shot was given.

These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.

You may report side effects to the FDA at 1-800-332-1088. You may also report side effects at https://www.fda.gov/medwatch.

If overdose is suspected:

If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

How do I store and/or throw out Firmagon?

  • If you need to store Firmagon at home, talk with your doctor, nurse, or pharmacist about how to store it.



  • NDC 55566-8403-1
  • FIRMAGON® 240mg*
    (degarelix for injection)
  • * 240 mg dose administered from
    two vials each containing 120 mg
  • For single use subcutaneous injection only
    Discard unused portion
  • Kit contents:
    2 vials each with 120 mg powder for injection
    2 syringes with Sterile Water for Injection, USP
    for reconstitution/administration
    2 vial adapters
    2 administration needles
  • Starting Dose
    Rx only



  • NDC 55566-8303-1
  • FIRMAGON® 80mg
    (degarelix for injection)
  • For single use subcutaneous injection only
    Discard unused portion
  • Kit contents:
    1 vial with 80 mg powder for injection
    1 syringe with Sterile Water for Injection, USP
    for reconstitution/administration
    1 vial adapter
    1 administration needle
  • Maintenance Dose (28 Days)
    Rx only


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