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.
Community Rating
No ratings yet
Compound Profile
Cetrorelix
Key Data
Research reference only
Research Focus
Preclinical data
⚠ 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)
In Plain English
Simple summaryCetrorelix (Cetrotide) is a synthetic GnRH antagonist used in assisted reproductive technology (ART) -- specifically to prevent premature LH surges that would cause premature ovulation before egg retrieval in IVF cycles. Unlike GnRH agonists (leuprolide, triptorelin) which require 1-2 weeks of priming and cause an initial hormone flare, cetrorelix works immediately upon first injection by competitively blocking GnRH receptors. This makes it ideal for the 'antagonist protocol' in IVF: it's started later in the stimulation cycle when follicles are growing and simply prevents premature ovulation until the trigger injection is given. FDA-approved since 2000, it's one of two approved GnRH antagonists for IVF (the other is ganirelix).
- 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
The full scientific detail, mechanisms, citations, and dosing data, follows below.
What is Cetrorelix?
Tap any underlined term for an instant definition.
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
By the Numbers
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. View all peptides' side effects →
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.
What the research doesn't show
Cetrorelix's limitation is that competitive antagonism can occasionally be overcome by very high endogenous GnRH concentrations -- 'escapes' are rare but possible if dosing is delayed. The need for daily injections until the trigger shot also requires patient compliance. In cancer patients needing fertility preservation before gonadotoxic chemotherapy, random-start protocols using cetrorelix allow immediate cycle start regardless of menstrual phase.
Medical Expert Videos
Physicians, researchers, and pharmacologists explain Cetrorelix, covering mechanisms of action, clinical context, and study findings.
Videos sourced from YouTube search. KnowYourPeptide does not endorse any individual creator. For research education only.
The Bottom Line
Cetrorelix has a growing body of preclinical evidence and a well-characterised safety profile in research settings. The most-studied application is: immediate competitive gnrh receptor blockade — suppresses lh surge within hours, without the 2-week flare seen with gnrh agonists.
The most commonly reported side effect in research subjects is injection site reactions — most common adverse effect. It is a research chemical, not approved for human use.
Frequently Asked Questions
Explore Further
Quick Reference
How It Compares
Ganirelix (Orgalutran) is the other approved GnRH antagonist for IVF and is essentially interchangeable with cetrorelix in clinical practice. Leuprolide and buserelin are GnRH agonists used in the 'long protocol' IVF approach -- more complex, longer duration, but historically considered to give slightly more predictable follicular synchronization. The antagonist protocol with cetrorelix or ganirelix has largely replaced the long protocol in many centers due to convenience and reduced OHSS risk.
Compare Cetrorelix side-by-sideResearch Use Only
This information is for educational research purposes only. This is not medical advice. Consult a qualified healthcare professional.