Cetrotide (cetrorelix) is a GnRH antagonist injection that blocks the premature LH surge during IVF stimulation, keeping your eggs in their follicles until your doctor retrieves them. In a standard antagonist protocol it is started around stimulation day 5–6 — when the leading follicle reaches about 14–15 mm — and continued until the trigger shot, typically for 4–7 days.
The data in this article comes from the FDA-approved Cetrotide prescribing information (DailyMed/NIH), a 2016 Cochrane review of 73 randomized controlled trials with 12,212 participants comparing GnRH antagonists with long agonist protocols, and a 2025 large cohort study of cetrorelix vs ganirelix. It was compiled by the ProIVF Medical Editorial Team and reviewed by the ProIVF Medical Advisory Board.
What Is Cetrotide and How Does It Work?
Cetrotide is the brand name for cetrorelix acetate, a gonadotropin-releasing hormone (GnRH) antagonist made by EMD Serono (Merck) and approved by the U.S. FDA for one specific job: preventing an early LH surge during controlled ovarian stimulation. It belongs to the same drug class as ganirelix (Orgalutran/Fyremadel), the other antagonist commonly used in IVF.
“CETROTIDE is indicated to inhibit premature luteinizing hormone (LH) surges in women undergoing controlled ovarian hyperstimulation (COH).” — FDA-approved Cetrotide prescribing information (DailyMed / U.S. National Library of Medicine)
Here is the problem it solves. As follicles grow and estrogen rises, the pituitary gland is triggered to release a surge of luteinizing hormone (LH). In a natural cycle that surge causes ovulation; in an IVF cycle, if it arrives before your scheduled retrieval, you can ovulate spontaneously and lose the eggs. Cetrotide blocks that surge by:
- Binding the GnRH receptors in the pituitary — competing with your body’s own GnRH so the “release LH” signal never gets through.
- Working fast — LH suppression begins within hours, with no lengthy down-regulation phase required first (as GnRH agonists need).
- Acting reversibly — pituitary function returns as soon as you stop, which is why the trigger shot works immediately after the last Cetrotide dose.
Because Cetrotide has no initial flare effect — unlike agonists, which briefly stimulate the pituitary before suppressing it — it does not cause the estrogen-withdrawal symptoms or ovarian cysts that some patients experience on long agonist protocols. This is a key reason the antagonist protocol, and Cetrotide with it, is now the standard at most IVF centers.
Where Does Cetrotide Fit in the IVF Timeline?
Cetrotide is used only during the ovarian stimulation phase, and only in protocols that include a GnRH antagonist. The full cycle looks like this:
| Stage | Timing | What happens |
|---|---|---|
| Pre-cycle prep (optional) | 1–4 weeks | Birth control pill or estrogen priming to synchronize follicles |
| Ovarian stimulation | 8–14 days | Daily FSH injections (e.g., Gonal-F, Menopur); Cetrotide starts around day 5–6 or when the leading follicle reaches 14–15 mm |
| Cetrotide (GnRH antagonist) | 4–7 days | Blocks the premature LH surge; daily 0.25 mg or a single 3 mg dose |
| Trigger shot (hCG or Lupron) | 1 day | Final egg maturation; retrieval 34–36 hours later |
| Egg retrieval | ~30 min | Follicles aspirated under anesthesia |
| Fertilization & culture | 3–6 days | IVF or ICSI (intracytoplasmic sperm injection); embryo grading |
| Embryo transfer | ~15 min | Fresh or frozen transfer |
| Luteal support | 2–10 weeks | Progesterone supporting implantation |
The key difference from a long agonist protocol: an agonist such as Lupron suppresses the pituitary for 1–3 weeks before stimulation begins, while an antagonist like Cetrotide is simply added mid-stimulation. That means no down-regulation phase, fewer total injections, and a shorter overall cycle.
How Is Cetrotide Dosed: 0.25 mg Daily or 3 mg Single Injection?
The FDA-approved prescribing information describes two regimens, both given by subcutaneous injection:
| Regimen | Dose | Timing | Typical use |
|---|---|---|---|
| Multi-dose (most common) | 0.25 mg once daily | Start on stimulation day 5–6, or when the leading follicle reaches 14–15 mm; continue through trigger day | Standard antagonist protocol worldwide |
| Single-dose | 3 mg once | One injection on stimulation day 7–8 | A single shot providing at least 4 days of protection |
According to the prescribing information, the 3 mg single dose was established in Phase 2 studies as the minimal effective dose with a protection window of at least 4 days, while 0.25 mg daily is the minimal effective dose of the multi-dose regimen. LH suppression is dose-dependent, and Cetrotide suppresses LH more strongly than FSH — exactly the goal: stop ovulation without interfering with follicle growth.
What this looks like in practice: most clinics use the 0.25 mg daily regimen. You keep taking your FSH injection in the morning and add the Cetrotide shot in the evening (or at a fixed time) — also subcutaneous, usually in the abdomen or thigh, rotating sites — until the trigger day. Because the antagonist holds the LH surge in check, your doctor can give the trigger shot (hCG or Lupron) as soon as the follicles are mature, and Cetrotide is simply stopped.
Never adjust the dose yourself. Start day, dose, and stop day must be set by your reproductive endocrinologist based on ultrasound and blood monitoring every 2–4 days during stimulation.
Cetrotide vs Ganirelix: Which GnRH Antagonist Is Better?
Cetrotide (cetrorelix) and ganirelix (Orgalutran/Fyremadel) are the two GnRH antagonists most used in IVF. They share the same mechanism and are largely interchangeable in practice, and a 2025 retrospective cohort study of 9,424 patients — 2,365 cetrorelix vs 7,059 ganirelix cycles after 1:3 propensity-score matching, a method that pairs similar patients to reduce bias — compared them directly:
- Live birth rates were comparable: 47.2% (cetrorelix) vs 49.4% (ganirelix), p = 0.074.
- Cetrorelix suppressed LH more strongly: LH ≥10 U/L in 4.9% vs 7.6% (p<0.001); trigger-day LH ratio ≥2 in 6.1% vs 9.2% (p<0.001).
- OHSS (ovarian hyperstimulation syndrome) was rarer with cetrorelix: 0.4% vs 1.1% (p = 0.01).
- Endometrial pattern favored cetrorelix: Type A lining (a favorable morphology) in 66.2% vs 60.1%.
The study authors concluded that both drugs deliver comparable live birth rates, but cetrorelix may suit patients at higher OHSS risk while ganirelix may fit cases needing rapid LH control. In everyday practice the choice usually comes down to clinic protocol, insurance coverage, and local availability — for most patients the outcomes do not differ meaningfully.
Does Cetrotide Change Your Chances of Getting Pregnant?
The question patients ask most is whether an antagonist protocol (Cetrotide) or a long agonist protocol (Lupron) works better, and the landmark 2016 Cochrane review — 73 randomized controlled trials, 12,212 participants — gives a clear answer. Two definitions make the table readable: an odds ratio (OR) compares the relative odds of an outcome between two groups, where below 1 means lower risk with the antagonist and above 1 means higher; the 95% confidence interval (CI) is the range in which the true effect most likely falls.
| Outcome | Antagonist vs Agonist | Evidence |
|---|---|---|
| Live birth rate | No significant difference (OR 1.02, 95% CI 0.85–1.23; 12 RCTs, n=2,303) | Moderate quality |
| OHSS (any grade) | Lower with antagonist (OR 0.61, 95% CI 0.51–0.72; 36 RCTs, n=7,944) — an 11% agonist risk becomes roughly 6–9% | Moderate quality |
| Miscarriage rate | No difference (OR 1.04, 95% CI 0.82–1.30; 33 RCTs, n=7,022) | Moderate quality |
| Cycle cancellation — OHSS risk | Lower with antagonist (OR 0.47, 95% CI 0.32–0.69) | — |
| Cycle cancellation — poor response | Higher with antagonist (OR 1.32, 95% CI 1.06–1.65) | Moderate quality |
In plain language: switching from a long agonist protocol to a Cetrotide-style antagonist protocol gives you the same chance of a live birth at roughly half the OHSS risk. The trade-off is that poor responders are slightly more likely to have a cycle cancelled for insufficient response — one reason doctors still choose a long protocol for specific cases such as endometriosis or diminished ovarian reserve. For a full comparison of stimulation options, see our IVF stimulation protocols guide.
What Are the Side Effects of Cetrotide?
Cetrotide is generally well tolerated. Per the FDA-approved labeling (adverse events occurring in ≥1% of 949 patients):
- Ovarian hyperstimulation syndrome (OHSS): 3.5% — this reflects the overall stimulation risk rather than the drug alone, and it is still lower than with agonist protocols (see the Cochrane data above).
- Nausea: 1.3%
- Headache: 1.1%
- Injection-site reactions: redness, bruising, itching, or swelling at the injection site — usually mild and transient.
Two further points from the labeling are worth knowing:
- Allergic reactions are rare but possible. One severe anaphylactic reaction (cough, rash, low blood pressure) was reported in a patient taking a much higher 10 mg/day dose for an unrelated condition — tell your doctor if you have a significant allergy history.
- No evidence of harm to babies. Follow-up of newborns born to the 316 women who used Cetrotide in the Phase 3 program found no concerning signal of congenital anomalies.
For practical tips on self-injecting — site rotation, reconstituting the powder, managing bruising — see our IVF injections guide and IVF medications guide.
How Much Does Cetrotide Cost?
Cetrotide is one of the pricier per-vial IVF medications, and cost varies widely by country, pharmacy, and insurance:
- United States (retail, without insurance): a typical multi-dose cycle of five 0.25 mg vials runs roughly $400–$800 depending on pharmacy pricing — substantially less with insurance or a savings program.
- China: Cetrotide 0.25 mg single vials cost about ¥500–¥900 (roughly $70–$130) at hospital or pharmacy prices.
- Thailand and other medical-travel destinations: usually below U.S. retail, and often bundled into the clinic’s stimulation medication package.
These are reference ranges, not quotes — your actual cost depends on your clinic’s negotiated pricing, insurance coverage, and whether medications are included in a package. For the bigger picture on medication spending, see our IVF fees breakdown and how much IVF costs guide.
What It Feels Like: Three Patients on Cetrotide
The following patient stories are shared with consent; names and identifying details have been changed to protect privacy.
Case 1 — “I barely noticed the daily Cetrotide shots — just the bruise.” Sarah, 34, has polycystic ovary syndrome (PCOS) and completed her first antagonist cycle at CNY Fertility in Colorado. “I was terrified of adding another injection. But the Cetrotide needle is tiny and subcutaneous — honestly, the FSH pen bothered me more. My clinic added evening Cetrotide on day 7, and my only complaint was a coin-sized bruise on my belly. We got 14 eggs, 7 embryos, and my first frozen transfer worked.” She paid about $640 for five Cetrotide vials at her local pharmacy using a savings card.
Case 2 — “My OHSS risk made me glad we chose the antagonist protocol.” Meghan, 29, is a high responder with an anti-Müllerian hormone (AMH) of 8.6. “My clinic flagged OHSS risk from the start, so we used low-dose FSH plus a Cetrotide antagonist protocol with a Lupron trigger. I still got mild OHSS — bloating and shortness of breath for a few days — but my doctor said a long agonist protocol could have been much worse. Cetrotide itself was the easiest part of the whole cycle.” She retrieved 24 eggs, and her first frozen embryo transfer resulted in a healthy daughter.
Case 3 — “It saved me a month of waiting.” Priya, 38, a poor responder, chose an antagonist protocol after learning about cycle length. “With the long protocol I would have had to down-regulate for two weeks before even starting stimulation. The antagonist protocol let us start in my very next cycle. Cetrotide was added on day 6, we triggered on day 11, and I loved how short everything was.” She had 5 eggs and 2 embryos, and a single-embryo transfer succeeded.
FAQ
Q: What does Cetrotide do in IVF?
Cetrotide (cetrorelix) is a GnRH antagonist that blocks the premature LH surge during stimulation, preventing ovulation before egg retrieval; it usually starts on stimulation day 5–6 — or when the leading follicle reaches 14–15 mm — and continues until the trigger shot. It is absorbed quickly, reaching peak blood levels about 1–2 hours after each injection.
Q: Is Cetrotide the same as ganirelix?
No — different molecules, but both GnRH antagonists used for the same purpose — a 2025 cohort of 9,424 patients found comparable live birth rates (47.2% vs 49.4%), with cetrorelix showing stronger LH suppression and less OHSS (0.4% vs 1.1%).
The choice is usually driven by clinic protocol and availability.
Q: How many days do you take Cetrotide?
Typically 4–7 days, from around stimulation day 5–6 until the trigger shot; if your follicles grow slowly, the course is longer. With the single 3 mg dose, one injection covers a protection window of at least 4 days.
Q: What is the difference between Cetrotide 0.25 mg and 3 mg?
0.25 mg is the daily multi-dose regimen (the standard worldwide), while 3 mg is a single-dose regimen — one injection providing at least 4 days of LH suppression for patients who want fewer shots. Both are FDA-approved, and most clinics use the daily 0.25 mg regimen.
Q: Does Cetrotide affect IVF success rates?
No — the 2016 Cochrane review of 73 RCTs (12,212 patients) found no difference in live birth rates between antagonist and long agonist protocols (OR 1.02, 95% CI 0.85–1.23, which includes 1 and is therefore not statistically significant). Cetrotide’s main benefit is a significantly lower OHSS risk (OR 0.61).
Q: What are the side effects of Cetrotide?
Per FDA labeling: OHSS 3.5%, nausea 1.3%, headache 1.1%, plus injection-site reactions (redness, bruising, itching) that are usually mild and transient.
Rotating injection sites reduces the discomfort; severe allergy is rare, and women allergic to cetrorelix, other peptide hormones, or mannitol should not use Cetrotide. Follow-up of 316 newborns found no concerning congenital anomaly signal.
Q: How much does Cetrotide cost?
In the US retail market, five 0.25 mg vials — a typical cycle — cost roughly $400–$800 without insurance; in China, about ¥500–¥900 per vial. Prices vary widely by pharmacy, insurance, and country, and a savings card can cut out-of-pocket cost significantly (Sarah in Case 1 paid about $640 for five vials).
Q: Can Cetrotide be used for egg freezing?
Yes — Cetrotide is used in controlled ovarian stimulation for both IVF and egg freezing, with the same mechanism and the same 0.25 mg daily dosing: blocking premature ovulation so the eggs are still there at retrieval.
Planning Your Stimulation Protocol
Choosing between an antagonist protocol (Cetrotide or ganirelix) and a long agonist protocol (Lupron) is a medical decision based on your age, ovarian reserve (AMH and antral follicle count), diagnosis, and history. The evidence is reassuring: antagonist protocols achieve the same live birth rates with a substantially lower OHSS risk.
High responders typically benefit most from an antagonist protocol, while some poor responders or endometriosis patients may still be offered a long protocol — ask each clinic how it tailors protocols to your profile. Our IVF stimulation protocols guide breaks down every option, and you can compare clinics that fit your needs in our IVF hospital directory.
This article was written by the ProIVF Medical Editorial Team and reviewed by the ProIVF Medical Advisory Board. It is based on publicly available data from the FDA-approved Cetrotide prescribing information (DailyMed/NIH), the 2016 Cochrane review of GnRH antagonists, and a 2025 peer-reviewed cohort study of cetrorelix vs ganirelix, to provide objective, accurate information for patients.
Medical disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified reproductive medicine specialist about your individual treatment plan. Last updated: August 14, 2026.
