GnRH antagonist injected daily during IVF stimulation to stop early ovulation; FDA-approved as Cetrotide since 2000.
Also called Cetrotide, Cetrorelix acetate
When Cetrorelix's status or evidence changes, it's in the next morning's email.
Cetrorelix is a 10-amino-acid peptide built from GnRH, the brain hormone that tells the pituitary to release LH and FSH, but changed at five positions so it blocks the GnRH receptor instead of switching it on. Unlike leuprolide or triptorelin, it causes no initial hormone surge. LH falls within 1 to 2 hours of a dose, and the effect wears off soon after the drug is stopped.
Its one approved use is in IVF and other fertility treatment. When the ovaries are stimulated to grow many follicles, rising estrogen can set off the body's own LH surge and release the eggs before they can be collected. A daily 0.25 mg injection of Cetrotide, started on day 5 or 6 of stimulation, prevents that. In the US label's three phase 3 studies, 0 to 1.9% of women had a premature LH surge.
A Cochrane review of 73 trials with 12,212 women found antagonist protocols give about the same live birth rate as the older long agonist protocol, with less ovarian hyperstimulation syndrome (OHSS). FDA approved Cetrotide in 2000, the EU in 1999, and the first US generic, from Qilu, on April 16, 2024. WADA does not name cetrorelix; its S2.2.1 entry covers GnRH agonists, not antagonists.
What it binds to, and what happens inside the body after that, step by step.
Cetrorelix competes with the body's own GnRH for receptors on the pituitary. With the receptors blocked, LH and FSH release drops in a dose-dependent way, with a stronger effect on LH. That stops the mid-cycle LH surge that would otherwise trigger ovulation during IVF stimulation. Because it blocks rather than overstimulates the receptor, there is no flare, and the pituitary recovers quickly after the last dose.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
Cetrorelix is an approved fertility drug tested in randomized trials against long agonist protocols. It almost always prevents premature LH surges, and antagonist protocols as a group match the long agonist protocol for live births while causing less OHSS. The evidence is limited to fertility treatment; it is not approved for any other use.
73 RCTs, 12,212 women comparing antagonist with long GnRH agonist protocols
Live birth was similar (odds ratio 1.02) and OHSS was less common with antagonists (odds ratio 0.61, about 6 to 9% vs 11%).
Read the study154 women having IVF: 115 given a single 3 mg cetrorelix dose, 39 given a triptorelin depot
No LH surge occurred on cetrorelix; it needed fewer stimulation days and caused less OHSS, with similar pregnancy rates but fewer eggs.
Read the study273 women having IVF (188 cetrorelix, 85 buserelin long protocol)
Moderate to severe OHSS was 1.1% with cetrorelix vs 6.5% with buserelin; pregnancy rates per cycle were 22% vs 26%.
Read the study9,424 women at one Chinese center (2,365 cetrorelix, 7,059 ganirelix), propensity matched
Live birth rates were similar (47.2% vs 49.4%); premature LH rises were less common on cetrorelix (4.9% vs 7.6%).
Read the study17 RCTs, 1,847 women in antagonist IVF cycles
Using an agonist instead of hCG to trigger after antagonist suppression cut OHSS (odds ratio 0.15) but lowered live birth in fresh transfers (odds ratio 0.47).
Read the studyNo preclinical studies are listed as key studies here. The human data above carries the evidence.
When a new Cetrorelix study in people is published, the daily email covers it.
These are questions the published research has not answered.
The US label says Cetrotide should be prescribed by doctors experienced in fertility treatment, and pregnancy must be ruled out before starting. Drugs@FDA lists the 3 mg single-dose vial as discontinued and the 0.25 mg vial as active; the first generic (Qilu, ANDA 217776, AP-rated) was approved on April 16, 2024. WADA's 2026 list does not name cetrorelix or GnRH antagonists: S2.2.1 covers GnRH and its agonist analogues in males.
When the FDA or WADA changes Cetrorelix's status, it's in the next morning's email.
How much of Cetrorelix is left after a single dose
Simple first-order model from the published half-life. Real clearance varies with dose, route, kidney and liver function and formulation. This is not a dosing schedule.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
A Cochrane review of 73 trials found no clear difference in live birth (odds ratio 1.02) and less OHSS with antagonists.
It lowers the risk compared with long agonist protocols, but moderate or severe OHSS still occurred in 3.5% of women in the label's studies. The bigger reduction comes from pairing it with an agonist trigger or freezing all embryos.
It is a receptor blocker. The label states no initial release of LH or FSH was detected; LH falls within 1 to 2 hours.
Follow-up of 316 babies born after Cetrotide found one case of anencephaly, one heart defect and one case of congenital glaucoma, with no pattern linking them to the drug. It is contraindicated in pregnancy; in rats, about 4 times the human dose caused complete embryo loss.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Cetrorelix blocks early ovulation, then a single GnRH agonist dose (triptorelin or leuprolide) replaces hCG to trigger egg maturation with much lower OHSS risk.
EvidenceCochrane review of 17 RCTs: OHSS odds ratio 0.15, but fewer live births in fresh transfers. Off-label in the US.
The labeled sequence: daily cetrorelix during stimulation, then hCG for final egg maturation.
EvidenceLabel-backed; clinical pregnancy rates of about 20 to 23% per attempt in the phase 3 studies.
Cetrotide 0.25 mg kit: refrigerated at 2 to 8°C (36 to 46°F), in the outer carton to protect from light.
Mix with the supplied 1 mL sterile water and use immediately.
One email when a trial reads out, a label changes or the FDA acts on a peptide. Free, every source linked, unsubscribe any time.