What is Degarelix?
Degarelix is a synthetic peptide GnRH (gonadotropin-releasing hormone) receptor antagonist approved for androgen deprivation therapy (ADT) in advanced prostate cancer. It consists of a modified decapeptide sequence that binds reversibly but with high affinity to pituitary GnRH receptors, immediately blocking the gonadotropin cascade that drives testicular testosterone synthesis. The result is a rapid, sustained reduction in serum LH, FSH, and testosterone without the initial hormonal surge that characterizes GnRH agonist therapy.
This absence of a testosterone flare distinguishes degarelix from GnRH agonists such as leuprolide. With agonist-based ADT, the initial receptor stimulation triggers a transient rise in testosterone (the 'flare') that can temporarily worsen bone pain, urinary obstruction, or spinal cord compression in men with metastatic disease. Because degarelix acts as a pure competitive antagonist from first dosing, testosterone suppression begins within days rather than weeks, and no flare occurs. In a pivotal Phase III trial of 610 patients, degarelix achieved testosterone levels at or below 0.5 ng/mL within three days in over 96% of subjects, compared to approximately three weeks required for leuprolide to reach castrate levels.
Degarelix was synthetically engineered to overcome the histamine-releasing properties that limited earlier GnRH antagonists such as abarelix. Its structural modifications result in very weak histamine-releasing activity, substantially reducing the risk of immediate hypersensitivity reactions that made earlier antagonists difficult to use in clinical practice. Upon subcutaneous administration, degarelix forms a gel-like depot at the injection site that releases the drug in a first-order manner, providing sustained pharmacological activity between monthly doses.
Beyond testosterone suppression, early data suggest that degarelix may offer cardiovascular advantages over GnRH agonists. Observational and retrospective analyses have found associations between degarelix use and lower rates of major adverse cardiovascular events compared to leuprolide, though prospective randomized data are still maturing. The PSA decline rate is also more rapid with degarelix, which may have prognostic relevance for monitoring treatment response.
Research Supply
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Dosage Guide
Route: Subcutaneous injection, abdominal region only; not available as oral formulation
Dosing Schedule
| Period | Dose |
|---|---|
| Loading dose (Day 1) | 240 mg (two 120 mg subcutaneous injections) |
| Maintenance dose | 80 mg subcutaneous injection every 28 days |
Reconstitution
Injection Volumes
| Dose | Volume | Syringe Units |
|---|---|---|
| 120 mg (x2 loading) | 3 mL per vial | Two separate injections, different sites |
| 80 mg (maintenance) | 4 mL | Single monthly injection |
Administration Tips
- Administer only by subcutaneous injection in the abdominal region
- Loading dose: both 120 mg injections must be given on Day 1 in different abdominal areas
- Maintenance: one 80 mg injection every 28 days
- Monitor serum testosterone prior to therapy and periodically during treatment
- Confirm maintenance of castrate testosterone levels below 50 ng/dL (0.5 ng/mL)
- Monitor PSA as a surrogate marker of disease response
Risks & Side Effects
Commonly Reported
Serious Risks
QT interval prolongation
Androgen deprivation in general is associated with QT prolongation. Use with caution in patients on QT-prolonging drugs or with baseline cardiac risk factors.
Bone mineral density loss
Chronic testosterone suppression leads to accelerated osteoporosis. Baseline and periodic bone density monitoring is recommended for patients on long-term ADT.
Metabolic effects
Insulin resistance, dyslipidemia, and increased cardiovascular risk are associated with long-term androgen deprivation therapy.
Depression and cognitive effects
Testosterone suppression can exacerbate depressive symptoms and may affect cognitive function. Monitor mental health during treatment.
Contraindications
- Known hypersensitivity to degarelix or any component of the formulation
- Use in women (not indicated; GnRH antagonists cause fetal harm)
- Pediatric use (not studied)
Frequently Asked Questions
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Experts Covering Degarelix
LEGAL DISCLAIMER
The information provided on this page is for educational and informational purposes only and is not intended as medical advice. Degarelix has not been approved by the FDA for any medical condition other than the treatment of advanced prostate cancer. Always consult with a qualified healthcare professional before starting any peptide therapy. Individual results may vary. Peptides Institute is not responsible for any adverse effects resulting from the use of information provided on this site.