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What Is Degarelix (Firmagon)?


Firmagon (degarelix) is a Gonadotropin Releasing Hormone (GnRH) receptor antagonist. It is indicated for use in individuals with advanced prostate cancer. Firmagon is administered as a subcutaneous (under the skin) injection in your abdominal area. Individuals taking Firmagon should also be monitored for cardiovascular complications, including disorder of the heart’s electrical activity.

What are the ingredients in Firmagon?

The active ingredient in Firmagon is degarelix, the Gonadotropin-Releasing Hormone (GnRH) receptor antagonist.

How does Firmagon work?

Firmagon’s active ingredient is a Gonadotropin-Releasing Hormone (GnRH) receptor antagonist. This means, that its purpose is to block the GnRH receptor. Prostate cancer tumors are often fueled to grow by androgens, including testosterone. Turning off the body’s ability to produce testosterone, or reducing the amount made can potentially halt tumor growth. Firmagon blocks a key receptor in the pathway to making testosterone. When this receptor is deactivated, it decreases luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are key in making testosterone. When the making of these hormones is suppressed, testosterone production is decreased as well. This is also known as medical or chemical castration.

What are the possible side effects of Firmagon?

Multiple clinical trials evaluated the safety and efficacy of Firmagon. The most common side effects of Firmagon include hot flashes, increased weight, decreased sex drive, erectile dysfunction, and increases in some liver enzymes. Injection site reactions are also possible while receiving Firmagon, and are typically accompanied by swelling, redness, and pain. This is not an exhaustive list of all potential side effects of Firmagon. Talk to your healthcare provider or pharmacist for further information.

Things to note about Firmagon

Several rare but more serious side effects can accompany Firmagon including serious allergic reactions and disorder of the heart’s electrical activity. Individuals should be closely monitored for signs of these serious conditions. Signs of a serious allergic reaction that should be brought to your provider’s attention immediately are:

  • Severe itching
  • Trouble breathing or wheezing
  • Swelling of your face, lips, mouth, or tongue

Before starting Firmagon talk to your provider if you:

  • Have any heart problems including long QT syndrome
  • Have problems with the levels of sodium, calcium, potassium, or magnesium in your blood
  • Have kidney or liver problems
  • Have any other medical conditions
  • Are currently taking any other medications, vitamins, or herbal supplements

Dosing information

Firmagon is administered as a subcutaneous injection (under your skin). Your healthcare provider will administered the injection for you into your abdomen. Your provider will help you determine the best dosage and administration schedule for your situation, however, a common dosage is 240 mg of Firmagon given as two 120 mg injections one time to start, followed by one 80 mg injection every 28 days.1

Written by: Casey Hribar | Last reviewed: January 2019
  1. Firmagon Prescribing Information. Jul 2016. Available from: