Summary
Degarelix is a ten amino acid GnRH receptor antagonist: it blocks the pituitary's receptor for GnRH, the brain hormone that switches on testosterone production, so testosterone falls to castrate levels (as low as after removal of the testes) within 3 days without the surge seen with agonists (drugs that first stimulate, then shut down, the same receptor) such as leuprolide. It has been FDA approved as Firmagon since December 2008 for advanced prostate cancer. In the 610 patient pivotal trial (the main trial behind approval), 97.2 to 98.3% of men on degarelix maintained castrate testosterone from day 28 through 1 year versus 96.4% on leuprolide, at the cost of injection site reactions in about 40%. It is prescription only and given as a monthly injection under the skin.
What is Degarelix?
Degarelix is a synthetic decapeptide GnRH (LHRH) receptor antagonist. It is also known as Firmagon, Degarelix acetate, FE200486.
How does it work?
Degarelix competitively blocks GnRH receptors on pituitary gonadotrophs, immediately suppressing LH and FSH release and therefore testicular testosterone production. Because it does not stimulate the receptor, there is no initial testosterone surge and no microsurge on repeat dosing. The subcutaneous depot forms a gel that releases drug over about a month.
| Cluster | Other peptides |
|---|---|
| Routes | Subcutaneous injection into the abdomen every 28 days (loading dose given as two injections) |
| Conditions studied | Advanced prostate cancer |
| Record | v3, draft, verified Sep 23, 2026 |
FDA-approved uses of Degarelix
Yes. Firmagon has been approved since December 2008, and its label has one use: treatment of patients with advanced prostate cancer. It is prescription only and is given in a clinic as a subcutaneous injection (under the skin) every 28 days. [2]
What does the evidence say about Degarelix?
One large randomized active controlled phase III trial. Klotz 2008 (n = 610): degarelix 240 mg loading dose followed by 80 mg or 160 mg monthly versus leuprolide 7.5 mg monthly for 12 months. Testosterone was 0.5 ng/mL or below from day 28 through day 364 in 97.2% (80 mg) and 98.3% (160 mg) versus 96.4% on leuprolide, meeting noninferiority. By day 3, 96% of degarelix patients were castrate versus none on leuprolide, and PSA fell faster. Injection site reactions occurred in about 40% versus under 1%.
| Evidence type | Indexed studies | Participants (human) |
|---|---|---|
| Human randomized trials | 1 | 610 |
| Human observational studies | 0 | n/a |
| Animal studies | 0 | n/a |
| All indexed studies | 1 | 610 |
Human evidence
Klotz 2008: 610 men with prostate cancer requiring androgen deprivation. Castration maintenance day 28 to 364: 97.2% with degarelix 240/80 mg, 98.3% with 240/160 mg, 96.4% with leuprolide. Day 3 castration: 96% versus 0%. Leuprolide patients had a testosterone surge in week 1 (median rise of about 65%) and PSA fell more slowly. Adverse events were similar apart from injection site reactions (about 40% on degarelix versus under 1%) and chills. Later pooled analyses suggested fewer cardiovascular events with antagonists in men with pre-existing cardiovascular disease, a hypothesis that dedicated trials have not confirmed.
Animal evidence
Preclinical rodent and primate studies established rapid, reversible testosterone suppression without a flare and characterized the depot pharmacokinetics. No carcinogenicity signal relevant to human dosing was found.
Key studies
| Study | Design and population | Outcome | Grade |
|---|---|---|---|
| The efficacy and safety of degarelix: a 12-month, comparative, randomized, open-label, parallel-group phase III study in patients with prostate cancer2008 PMID 19035858 | Randomized, open label, active comparator noninferiority trial, 12 monthsn = 610 Men with histologically confirmed prostate cancer requiring androgen deprivation therapy | Testosterone 0.5 ng/mL or below from day 28 to 364 in 97.2% (240/80 mg) and 98.3% (240/160 mg) versus 96.4% with leuprolide; castration by day 3 in 96% versus 0%; injection site reactions about 40% versus under 1% | Evidence: Human RCT evidence |
Conditions studied
| Condition | Grade | Note |
|---|---|---|
| Advanced prostate cancer | Evidence: Human RCT evidence | Castration by day 3 in 96% versus 0% with leuprolide, maintained through a year in about 97 to 98%; injection site reactions in about 40%; FDA approved as Firmagon. |
Is Degarelix legal in the United States?
FDA and compounding status
FDA approved as Firmagon in December 2008 for advanced prostate cancer. No generic is available as of the last verified date. Because an approved product exists, compounding is not permitted beyond patient specific exceptions.
WADA status
Not WADA prohibited. Not named on the current prohibited list. Athletes should still confirm against the list in force for their season.
Regulatory timeline
- FDA
FDA approves Firmagon (degarelix) for advanced prostate cancer
FDA approved degarelix injection (Firmagon), a GnRH receptor antagonist peptide, for adults with advanced prostate cancer.
Regulatory: FDA approvedSource: Drugs@FDA: Firmagon (degarelix) NDA 022201
Degarelix dose on the FDA label
Doses below are quoted from the FDA label for its approved uses, plus the doses used in the pivotal trials where noted. The prescriber sets the dose; PeptideAgent does not recommend doses or protocols.
FDA label (Firmagon, DailyMed; subcutaneous injection in the abdomen by a healthcare professional only): starting dose 240 mg given as two injections of 120 mg, then a maintenance dose of 80 mg as a single injection every 28 days, with the first maintenance dose 28 days after the starting dose. The pivotal trial (Klotz 2008) used the same regimen.
Routes reported
| # | Route |
|---|---|
| 1 | Subcutaneous injection into the abdomen every 28 days (loading dose given as two injections) |
What are the side effects and interactions of Degarelix?
Side effects
| # | Reported side effect |
|---|---|
| 1 | Injection site pain, erythema, swelling, or nodules (about 40% of patients, mostly after the loading dose) |
| 2 | Hot flashes (about 26% in the pivotal trial) |
| 3 | Weight gain, fatigue, and increased liver transaminases |
| 4 | Chills and fever in the first days |
| 5 | Loss of libido and erectile dysfunction |
| 6 | Bone density loss and fracture risk with prolonged androgen deprivation |
| 7 | QT prolongation |
| 8 | Hyperglycemia and increased cardiovascular risk with long term androgen deprivation |
Interactions
| # | Interaction |
|---|---|
| 1 | QT prolonging drugs (class IA and III antiarrhythmics, some antipsychotics and antibiotics): additive risk |
| 2 | Antidiabetic drugs: glucose control may worsen during androgen deprivation |
| 3 | No CYP450 mediated interactions identified in vitro |
Contraindications
| # | Contraindication |
|---|---|
| 1 | Hypersensitivity to degarelix |
| 2 | Women (not indicated; may cause fetal harm) |
| 3 | Use with caution in congenital long QT syndrome, electrolyte abnormalities, or heart failure |
How do people access Degarelix legally?
Typical cost: Roughly 600 to 900 USD per monthly 80 mg maintenance injection at list price, with the 240 mg loading dose about twice that. Insurance and Medicare Part B cover it for prostate cancer.
Verified access options
Step 1
Prescription from a urologist or oncologist, administered in clinic as a monthly subcutaneous injection.
Step 2
Not available through compounding or telehealth peptide clinics.
Access paths are verified against public regulatory records and prescriber licensing. We never list unlicensed vendors.
Compare Degarelix
Frequently asked questions
How fast does degarelix lower testosterone?
Within days. In the 610 patient pivotal trial, 96% of men on degarelix reached castrate testosterone by day 3, compared with none on leuprolide, which caused a testosterone surge in the first week before suppression. From day 28 through 1 year, 97 to 98% of degarelix patients stayed castrate versus 96.4% on leuprolide. [1]
What are the side effects of degarelix?
Injection site pain, redness, and swelling affect about 40% of patients, mostly after the large loading dose, and chills can occur in the first days. Beyond that the effects are those of low testosterone: hot flashes (about 26%), weight gain, fatigue, loss of libido, erectile dysfunction, bone loss, and higher diabetes and cardiovascular risk with long term use. Liver enzyme elevations and QT prolongation are also on the label. [1] [2]
What is the degarelix (Firmagon) dose on the FDA label?
A 240 mg starting dose given as two 120 mg injections under the skin of the abdomen, then 80 mg once every 28 days. A healthcare professional gives every dose, in areas of the abdomen away from waistbands and ribs. Because degarelix blocks GnRH receptors directly, it does not cause the testosterone flare seen with GnRH agonists, so no antiandrogen cover is needed. [1] [2]
How much does degarelix cost?
Roughly 600 to 900 USD per monthly maintenance injection at list price, and about double for the loading dose. Insurance and Medicare Part B cover it for prostate cancer. No generic exists. Prices were checked on the last verified date. [2]
Is degarelix banned by WADA?
It is not named on the WADA Prohibited List. Section S2 prohibits GnRH and its analogs in males, and WADA's examples are all agonists; degarelix is an antagonist that lowers testosterone and has no performance rationale. Athletes on it for cancer should still notify their anti-doping organization and consider a therapeutic use exemption. [3]
Degarelix vs leuprolide: which is better?
Both keep about 96 to 98% of men castrate through a year. Degarelix works within 3 days with no flare, so it is preferred when a testosterone surge could cause spinal cord compression or urinary obstruction, and it lowers PSA faster. Leuprolide is cheaper, has 3 to 6 month depots, and causes far fewer injection site reactions (under 1% versus about 40%). [1]
Decisions about starting, stopping, or combining any treatment belong with a licensed clinician who knows your history.
Sources
Numbered citations above point to these primary sources. PubMed entries link to the indexed abstract.
- [1]Klotz L et al. The efficacy and safety of degarelix: a 12-month, comparative, randomized, open-label, parallel-group phase III study in patients with prostate cancer. BJU Int 2008PubMed 19035858, 2008
- [2]FDA prescribing information for Firmagon (degarelix for injection), via DailyMedFDA, 2024
- [3]WADA Prohibited List, section S2 (GnRH and its analogs in males)WADA, 2026
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<a href="https://peptideagent.ai/peptides/degarelix">Degarelix: evidence, legality, and access</a>, PeptideAgent, updated September 23, 2026.