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GnRH Agonist (LHRH Analogue) Pregnancy: Contraindicated — causes fetal harm. Effective non-hormonal contraception required in premenopausal women during treatment.

Goserelin

Brand names: Zoladex

Adult dose

Dose: Prostate cancer / endometriosis / uterine fibroids: 3.6mg SC implant every 28 days, OR 10.8mg SC implant every 12 weeks (3-monthly). Breast cancer (premenopausal): 3.6mg SC every 28 days.
Route: Subcutaneous implant (abdominal wall — pre-loaded syringe)
Frequency: Every 28 days (3.6mg) or every 12 weeks (10.8mg)
Max: 10.8mg per 12-week depot
Continuous GnRH agonism suppresses LH/FSH after initial flare (paradoxical receptor downregulation). Initial flare: testosterone/oestrogen rises in first 1–2 weeks (risk of tumour flare in prostate cancer — anti-androgen cover with bicalutamide for 2–4 weeks before starting). Endometriosis: maximum 6 months continuous use — bone loss risk with prolonged use (add-back HRT if >6 months needed).

Paediatric dose

Route: Subcutaneous implant
Frequency: Every 28 days
Max: 3.6mg per month
Used for central precocious puberty under specialist paediatric endocrinology supervision. Dose individualised — seek specialist opinion.

Dose adjustments

Renal

No dose adjustment required.

Hepatic

No dose adjustment required.

Clinical pearls

  • Tumour flare prevention in prostate cancer: start bicalutamide (anti-androgen) 3–7 days BEFORE or concurrent with first goserelin implant, continue for 4 weeks — prevents tumour flare (pain, urinary obstruction, spinal cord compression)
  • Bone protection in long-term use: prescribe calcium, vitamin D, and consider bisphosphonate/denosumab for all men on androgen deprivation therapy >6 months (NICE)
  • Endometriosis: 6-month courses with add-back HRT (tibolone or low-dose oestrogen/progestogen) to mitigate bone loss in longer use
  • Fertility preservation: sperm banking (men) or ovarian reserve discussion (women) before starting GnRH agonist therapy

Contraindications

  • Pregnancy (risk of fetal harm)
  • Undiagnosed vaginal bleeding
  • Hypersensitivity to goserelin or GnRH analogues

Side effects

  • Hot flushes and sweating (chemical menopause/castration)
  • Reduced libido and sexual dysfunction
  • Vaginal dryness (women)
  • Erectile dysfunction (men)
  • Bone mineral density reduction (osteoporosis risk — long-term use)
  • Tumour flare (prostate cancer — first 1–2 weeks)
  • Injection site bruising/pain
  • Mood changes, depression
  • Glucose intolerance / metabolic syndrome (men — androgen deprivation therapy)

Interactions

  • Antidiabetic drugs — GnRH agonist-induced metabolic changes may worsen glycaemic control
  • QT-prolonging drugs — androgen deprivation therapy prolongs QT; additive risk

Monitoring

  • Testosterone (men) / oestradiol (women) — confirm castrate levels
  • PSA (prostate cancer)
  • Bone mineral density (DEXA) annually if long-term use
  • Blood glucose, HbA1c (metabolic monitoring in men)
  • ECG (QT monitoring if risk factors)

Reference: BNFc; BNF 90; NICE NG131 (Prostate Cancer); ESHRE Endometriosis Guideline 2022. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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