GnRH Agonist (LHRH Analogue) Pregnancy: Contraindicated in pregnancy and breast-feeding — theoretical risk of abortion or foetal abnormality. Exclude pregnancy before treatment; use non-hormonal contraception during therapy until menses resume.

Goserelin

Brand names: Zoladex

Goserelin is a gonadotrophin-releasing hormone (GnRH) agonist depot implant used in prostate and breast cancer, endometriosis and assisted reproduction.

Adult dose

Dose: One 3.6 mg depot (Zoladex 3.6 mg implant)

Route: Subcutaneous injection into the anterior abdominal wall

Frequency: Every 28 days

UK SPC (Zoladex 3.6 mg Implant). Adults: one 3.6 mg depot injected subcutaneously into the anterior abdominal wall every 28 days. No dosage adjustment for renal or hepatic impairment or in the elderly. Not indicated for use in children. Indication-specific duration: Breast cancer — when combined with an aromatase inhibitor, initiate the LHRH agonist at least 6–8 weeks before the aromatase inhibitor and continue without interruption; confirm premenopausal status before starting. Endometriosis — treat for 6 months only; do not repeat courses (bone mineral density loss). Endometrial thinning — 4 or 8 weeks' treatment (a second depot may be needed). Uterine fibroids with anaemia — 3.6 mg depot with supplementary iron for up to 3 months before surgery. Assisted reproduction — used to downregulate the pituitary (usually 7–21 days) before controlled ovarian stimulation. Caution injecting near the inferior epigastric artery; extra care with low BMI or full anticoagulation. US labelling (ZOLADEX 3.6 mg) concurs: 3.6 mg SC every 28 days.

Dose adjustments

Renal

No dosage adjustment necessary for patients with renal or hepatic impairment.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any excipient
Pregnancy and lactation (see section 4.6)

Side effects

Hot flush (very common)
Hyperhidrosis / sweating (very common)
Libido decreased (very common)
Injection site reactions
Mood changes, depression (common)

Interactions

Medicinal products that prolong the QT interval — androgen deprivation therapy may prolong the QT interval; assess benefit-risk including Torsade de pointes risk before initiating
Diagnostic tests of pituitary-gonadotropic and gonadal function may be misleading during treatment and until menses resume (US labelling)

Clinical monograph

How it works

Continuous GnRH receptor stimulation initially raises then suppresses pituitary gonadotrophin output, ultimately lowering testosterone or oestradiol to castrate levels.

Prescribing in practice

In prostate cancer an initial testosterone surge can cause tumour flare, so co-administer an anti-androgen around initiation in those at risk of spinal cord compression or ureteric obstruction.
Long-term use reduces bone mineral density; consider bone protection and cardiovascular risk in prolonged androgen deprivation.
Administer the depot by subcutaneous implant at the scheduled interval as directed in current prescribing references.

Monitoring

Monitor testosterone or oestradiol suppression and treatment response, with attention to bone density during prolonged therapy.

Counselling the patient

Hot flushes, reduced libido and sexual dysfunction are common; report bone pain or new urinary symptoms early.
Attend appointments on time so depot injections are not delayed.
Menstruation usually stops during treatment and returns after stopping in pre-menopausal women.

Evidence & guidelines

GnRH agonists are a cornerstone of androgen deprivation in prostate cancer and are recommended in NICE and international guidance.

Reference: NICE NG131 (Prostate Cancer); ESHRE Endometriosis Guideline 2022; 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.

Pathways