Pharmacology · GnRH analogues (agonists and antagonists)
Degarelix !
A monthly injection for advanced prostate cancer that blocks the pituitary GnRH receptor. Testosterone falls quickly, without the flare caused by agonists.
Updated 2026-11-01
Mechanism of action
Degarelix is a peptide GnRH receptor antagonist. It binds the pituitary GnRH receptors and blocks them directly, so LH and FSH fall at once and testosterone drops to castration levels quickly. Because it never stimulates the receptor, there is no initial surge of testosterone (no flare).
- Binds and blocks the pituitary GnRH receptor
- LH and FSH fall at once
- Testosterone drops quickly to castration levels
- No initial testosterone flare
Pharmacokinetics
- Absorption
- Injected under the skin of the abdomen, where it forms a depot gel that releases it slowly
- Elimination
- Broken down into peptides; eliminated through the liver and bile, and partly in the urine
Indications
- Advanced prostate cancer Prostate cancer →
Adverse effects
Common
- Injection-site pain, redness, swelling or hardness
- Hot flushes and sweating
- Weight change
- Tiredness, dizziness and headache
- Raised liver enzymes
Contraindications
- Hypersensitivity to degarelix
- Pregnancy (not indicated in women)
Key interactions
- Drugs that prolong the QT interval
- Additive QT prolongation.
What is monitored
- Testosterone and PSA
- ECG and electrolytes when there is QT risk
- Bone health with long treatment
Administration and safety
- Powder reconstituted with its liquid and injected under the skin of the abdomen by a health professional, usually every 28 days.
- After the injection, belts and waistbands should not press on the site.
Nursing care
- Ask about long QT syndrome and low or high potassium, calcium, magnesium or sodium before starting.
- Inject into the abdomen away from the ribs and waistline, and rotate sites; local reactions are common.
- Teach to report palpitations, fainting or swelling of the face and throat.
- Check the injection site at the next visit; local reactions are the most common effect.
Pregnancy and breastfeeding
Not used in women; it may harm a fetus.
Test yourself
Think of the answer, then tap the question to see it.
Why does degarelix not cause a tumour flare in prostate cancer?
It is a GnRH receptor antagonist: it blocks the receptor from the start instead of first stimulating it, so testosterone never surges.
Which ECG change is a concern with degarelix?
QT prolongation; risk factors such as long QT syndrome and electrolyte imbalances are checked.
What is the most common adverse effect of degarelix injections?
Injection-site reactions: pain, redness, swelling or hardness where it was injected.
Related drugs
Related conditions
← Back to the class: GnRH analogues (agonists and antagonists)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Degarelix Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 46 (McGraw Hill, 2023).
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Representative model, for educational purposes only.