Cetrorelix
Cetrorelix is a 10-aa synthetic GnRH antagonist that immediately blocks GnRH receptors, suppressing LH and FSH without the initial testosterone flare of GnRH agonists. FDA-approved for controlled ovarian stimulation in IVF.
⚠ Research & Educational Use Only. Cetrorelix is a research chemical documented here for scientific education. All information references peer-reviewed literature and preclinical/clinical study data. Not for human consumption. Not medical advice. Consult a licensed researcher or healthcare professional before any laboratory use.
- Immediate competitive GnRH receptor blockade — suppresses LH surge within hours, without the 2-week flare seen with GnRH agonists
- Prevents premature LH surges during controlled ovarian stimulation (COS) — a critical limitation that was solved by GnRH antagonists
- FDA-approved for COS in IVF — standard of care in European and US fertility practice
- Cetrorelix is not FDA-approved for human use. FDA-approved prescription drug (Cetrotide, Merck KGaA/EMD Serono). Indicated for controlled ovarian stimulation with COS protocols.
Research At a Glance
- Immediate competitive GnRH receptor blockade — suppresses LH surge within hours, without the 2-week flare seen with GnRH agonists
- Prevents premature LH surges during controlled ovarian stimulation (COS) — a critical limitation that was solved by GnRH antagonists
- FDA-approved for COS in IVF — standard of care in European and US fertility practice
- Shorter treatment protocol vs GnRH agonist (3-4 days vs 2-4 weeks of pre-treatment)
What is Cetrorelix?
Cetrorelix (brand name: Cetrotide) is a synthetic decapeptide and competitive GnRH receptor antagonist developed by Zentaris. It received FDA approval in 2000 for controlled ovarian stimulation in IVF, becoming one of the first GnRH antagonists approved for clinical use.
Cetrorelix was developed as a structurally modified version of GnRH (decapeptide) with substitutions at positions 1, 2, 3, 6, and 10 that convert the GnRH agonist into a competitive antagonist. The modified amino acids include D-amino acid substitutions (D-Phe, D-Pal, D-Cpa) that provide GnRH receptor binding without activation, creating competitive blockade.
**Mechanism — immediate vs delayed suppression:** Unlike GnRH agonists (which require 2-4 weeks of continuous exposure to downregulate the pituitary through receptor desensitization), GnRH antagonists like cetrorelix produce **immediate competitive blockade** of GnRH receptors: - Within 6 hours of a 3 mg SC dose: LH suppression begins - Within 24 hours: LH is suppressed by >80%, preventing spontaneous LH surge - No initial flare — testosterone (or estradiol) does not spike
**Significance in ART (Assisted Reproductive Technology):** Before GnRH antagonists were available, IVF cycles required 2-4 weeks of GnRH agonist pre-treatment to suppress the pituitary before FSH stimulation could begin (the "long-down protocol"). This was necessary to prevent premature LH surge, which would trigger early ovulation and destroy the cohort of developing follicles.
Cetrorelix and ganirelix allowed the development of the "antagonist protocol" (also called the "GnRH antagonist-short protocol"), in which ovarian stimulation with FSH begins immediately and cetrorelix is added only when follicles reach a critical size to prevent the LH surge. This protocol is now used in approximately 50% of IVF cycles globally, offering
- Shorter stimulation duration (10-12 days vs 20-30 days for long agonist protocol)
- Lower OHSS risk
- No risk of hypoestrogenic side effects from prolonged pituitary suppression
- Equal or better live birth rates in most patient populations
Key Research Benefits
Documented effects observed in preclinical and clinical studies on Cetrorelix. See all Hormonal Health peptides for comparison.
Side Effects & Risks
Adverse effects reported in the research literature. All data sourced from preclinical and clinical study reports.
Dosing Data from the Literature
Doses referenced below are sourced from published preclinical and clinical studies. Use the peptide dose calculator to convert these values to injection volume.
Cetrorelix (Cetrotide) for controlled ovarian stimulation:
Multiple dose protocol (0.25 mg/day): - Start: SC 0.25 mg/day beginning on cycle day 5-6 of FSH stimulation - Continue daily until hCG trigger injection - Prevents premature LH surge throughout the stimulation window
Single dose protocol (3 mg once): - SC 3 mg on cycle day 7 (or after 6 days of FSH) - Provides ~4 days of LH suppression; additional 0.25 mg/day if oocyte retrieval not planned within 4 days
Administration in Research Settings
Standard reconstitution and administration methodology for laboratory research use.
SC injection into the lower abdomen, rotating sites. The 0.25 mg/vial powder is reconstituted with 1 mL water for injection. Inject immediately after reconstitution. Do not mix with FSH injection.
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Research Use Only
This information is for educational research purposes only. This is not medical advice. Consult a qualified healthcare professional.