GnRH antagonist Pregnancy: There is no relevant indication for use of FIRMAGON in women. Fertility: FIRMAGON may inhibit male fertility for as long as testosterone is suppressed (SPC §4.6).

Degarelix

Brand names: Firmagon

Degarelix is a gonadotrophin-releasing hormone (GnRH) receptor antagonist given by subcutaneous injection to achieve androgen deprivation in advanced hormone-dependent prostate cancer.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: Starting dose 240 mg, given as two consecutive subcutaneous injections of 120 mg each; maintenance dose 80 mg as one subcutaneous injection monthly

Route: Subcutaneous injection into the abdominal region ONLY — not to be administered intravenously; intramuscular administration is not recommended as it has not been studied

Frequency: Single 240 mg starting dose, then 80 mg monthly — the first maintenance dose should be given one month after the starting dose

UK SPC (Degarelix Ferring 80 mg powder and solvent for solution for injection / FIRMAGON) §4.2. May be used as neo-adjuvant or adjuvant therapy in combination with radiotherapy in high-risk localised and locally advanced prostate cancer. The therapeutic effect should be monitored by clinical parameters and prostate specific antigen (PSA) serum levels; if the clinical response appears sub-optimal, confirm that serum testosterone levels remain sufficiently suppressed. Because degarelix does not induce a testosterone surge, it is not necessary to add an anti-androgen as surge protection at initiation of therapy. Must be reconstituted prior to administration (see SPC §6.6). Vary the injection site periodically and inject in areas that will not be exposed to pressure (not close to a waistband or belt, not close to the ribs). Cross-check — US labelling gives the same doses with the maintenance injection once every 28 days: starting dose 240 mg as two subcutaneous injections of 120 mg at a concentration of 40 mg/mL (each 120 mg vial reconstituted with 3 mL Sterile Water for Injection); maintenance 80 mg as one subcutaneous injection at 20 mg/mL (vial reconstituted with 4.2 mL, 4 mL withdrawn). Reconstituted drug must be administered within one hour; do not shake the vials; administration by a healthcare professional only. Paediatric: there is no relevant use of FIRMAGON in children and adolescents in the treatment of adult male patients with advanced hormone-dependent prostate cancer.

Dose adjustments

Renal

There is no need to adjust the dose in patients with mild or moderate kidney (or liver) function impairment. Patients with severe liver or kidney impairment have not been studied and caution is therefore warranted (SPC §4.2, §4.4).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to degarelix or to any of the excipients

Side effects

Hot flushes (very common — 25% of patients treated for one year)
Injection site reactions — mainly pain (28%) and erythema (17%), less frequently swelling (6%), induration (4%) and nodule (3%); these occur primarily with the starting dose and are mostly transient and mild to moderate
Weight increase (very common — 7%)
Transient chills, fever or influenza-like illness hours after dosing (3%, 2% and 1% of patients respectively)
Increased liver transaminases (common); anaemia (very common); hyperhidrosis including night sweats and rash (common)
Cardiac arrhythmia including atrial fibrillation, palpitations and QT prolongation (uncommon); myocardial infarction and cardiac failure (rare)

Interactions

No formal drug-drug interaction studies have been performed; degarelix is not a substrate for the human CYP450 system and is neither an inducer nor an inhibitor of it in vitro, so clinically significant CYP450 pharmacokinetic interactions are unlikely (US PI §7)
Medicines that may prolong the QT interval — long-term androgen deprivation therapy may prolong the QTc interval, so the benefit/risk ratio must be thoroughly appraised in patients receiving such products, in patients with a history of a corrected QT interval over 450 msec, and in patients with a history of or risk factors for torsades de pointes (SPC §4.4; §4.5 was truncated at the source fetch limit)

Clinical monograph

How it works

It binds GnRH receptors in the pituitary directly and reversibly, rapidly suppressing luteinising hormone and testosterone without the initial surge seen with GnRH agonists.

Prescribing in practice

Unlike GnRH agonists it does not cause an initial testosterone flare, so no antiandrogen cover is required, but injection-site reactions are common.
Hot flushes, weight gain and other consequences of androgen deprivation occur and long-term bone and metabolic health should be considered.
Caution is advised in patients with QT-interval prolongation or relevant cardiovascular disease.

Monitoring

Monitor testosterone and prostate-specific antigen response, with attention to injection-site reactions and cardiovascular and bone health on long-term therapy.

Counselling the patient

Injection-site redness, swelling or pain is common, especially after the first dose, and usually settles.
Hot flushes and tiredness are expected effects of lowering testosterone.
Keep regular appointments so your treatment response can be checked.

Evidence & guidelines

A pivotal randomised trial showed degarelix achieved faster testosterone suppression than leuprorelin while avoiding the testosterone surge.

Reference: NICE NG131; ESMO prostate cancer; BAUS; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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