Quick summary
Buserelin (Suprefact) is a GnRH superagonist 20-170x more potent than native GnRH, approved in Europe and Canada for prostate cancer, endometriosis, and IVF. It suppresses sex steroids to castrate levels via pituitary desensitization.
Overview
Buserelin is a synthetic GnRH agonist peptide widely approved in Europe, Canada, and other regions under brand names including Suprefact and Suprecur for prostate cancer, endometriosis, and female infertility. It is not approved in the United States but is a first-line hormonal therapy in many countries. Available as subcutaneous injection, nasal spray, or implant, it achieves sex steroid suppression equivalent to surgical castration through pituitary GnRH receptor desensitization.
Mechanism of action
Buserelin is a GnRH superagonist with approximately 20–170 times the potency of endogenous GnRH for stimulating LH and FSH secretion. Structural modifications — D-serine(tBu) at position 6 and ethylamide at the C-terminus — confer enzymatic stability and high receptor binding affinity. Initial administration triggers an LH/FSH flare response. With continuous exposure (unlike pulsatile endogenous GnRH), buserelin maintains constant GnRH receptor occupancy, inducing receptor downregulation and uncoupling. Within 2–4 weeks, pituitary gonadotrophs become desensitized, LH and FSH secretion collapses, and gonadal testosterone or estradiol falls to castrate levels. In prostate cancer, androgen withdrawal inhibits androgen receptor signaling that drives tumor proliferation.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| Prostate cancer — ADT | subcutaneous | 500–500 mcg | three times daily for 7 days, then nasal maintenance | Initial: 500 mcg SC three times daily x7 days. Maintenance: nasal spray 400 mcg into each nostril 3x/day (total 1200 mcg/day). Or switch to implant. |
| Endometriosis / IVF down-regulation | nasal | 300–900 mcg | two to three times daily | Dose varies by indication and protocol. IVF down-regulation typically 200–400 mcg twice daily until pituitary suppression confirmed. Endometriosis: 6-month course. |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
European clinical trials established buserelin as effective ADT for advanced prostate cancer, achieving castrate testosterone in >95% of patients within 4 weeks. Long-term (3-year) data demonstrate disease stabilization comparable to orchiectomy. For endometriosis, 6-month nasal spray or implant treatment reduces lesion extent and pain scores significantly. In IVF protocols, buserelin down-regulation is used in the long protocol to synchronize follicular development, though GnRH antagonists are increasingly preferred due to shorter treatment duration. Buserelin's clinical profile is similar to leuprolide and other GnRH agonists in its class.[1][2][3][4]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with Buserelin for synergistic effects.
Legal status
Not FDA-approved; approved by EMA and health authorities in the UK, Canada, Germany, France, and numerous other countries. Indicated for prostate cancer, endometriosis, and female infertility in approved jurisdictions. Prescription-only throughout all jurisdictions where available.
Sourcing & access
Prescription required
Buserelin is an FDA-approved prescription medication available through licensed healthcare providers, telehealth platforms, and 503A/503B compounding pharmacies.
Frequently asked questions
Buserelin is a synthetic GnRH agonist peptide approved in Europe, Canada, and other regions under brand names Suprefact and Suprecur for prostate cancer, endometriosis, and female infertility. It is not approved in the United States.
Buserelin is a GnRH superagonist 20 to 170 times more potent than native GnRH. Initial administration triggers an LH/FSH flare, but continuous exposure causes receptor downregulation and pituitary desensitization, suppressing sex steroids to castrate levels within 2 to 4 weeks.
Buserelin is available as subcutaneous injection for induction phases, nasal spray for maintenance and down-regulation, and implant formulations for sustained release. The subcutaneous route is typically used for the first 7 days of prostate cancer therapy, while the nasal spray at 200 to 400 mcg per nostril is commonly used for endometriosis and IVF down-regulation protocols.
Common side effects include hot flashes, sexual dysfunction, initial disease flare in prostate cancer, bone mineral density loss with long-term use, nasal irritation from the spray, headache, fatigue, and mood changes.
Research references
- Buserelin GnRH agonist in prostate cancer: clinical pharmacology and efficacyPubMed
- Buserelin versus orchiectomy in advanced prostate cancer: randomized trialPubMed
- GnRH agonists in endometriosis: meta-analysis of efficacyPubMed
- Buserelin IVF protocol: pituitary downregulation and ovarian stimulationPubMed