Ganirelix (Orgalutran)_Dosage, benefits & legal status
Also known as Antagon, Orgalutran, Fyremadel, Ganirest, Ganirelix Gedeon Richter, Ganirelix Acetate Injection, ganirelix acetate, Org 37462, RS-26306, RS-26306-298
A ten-residue GnRH blocker injected once a day during IVF stimulation to prevent an early LH surge. FDA-approved since July 29, 1999, with seven US generic approvals since 2018.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Ganirelix (Orgalutran)?
Plain language first. The technical label stays, but it never stands alone.Overview
In IVF the ovaries are stimulated to ripen several eggs at once, and the body's own LH surge can release them before they are collected. A daily ganirelix injection, started partway through stimulation, holds that surge back: in the European pivotal trial a premature surge occurred in under 1% of 463 women, treatment lasted a median 5 days against 26 with the older buserelin approach, and ovarian hyperstimulation occurred in 2.4% against 5.9%. The trade-off in the original trials was slightly fewer eggs and numerically lower ongoing pregnancy rates (20.3% against 25.7% with buserelin, and 30.8% against 36.4% with leuprolide).
Ganirelix is a synthetic decapeptide derived from GnRH, with an N-acetyl cap and substitutions at positions 1, 2, 3, 6, 8 and 10: three D-form aromatic residues at the front, diethyl-D-homoarginine at 6, diethyl-L-homoarginine at 8 and D-alaninamide at 10. It competitively blocks GnRH receptors on the pituitary cells that release LH and FSH, lowering LH more than FSH within hours and without the initial flare seen with agonists such as leuprolide; levels recover within 48 hours of stopping. Organon developed it as Org 37462, and the FDA approved it as Antagon on July 29, 1999, the first GnRH antagonist approved in the US.
What it's used for
A daily injection under the skin during IVF and other controlled ovarian stimulation, to stop an early LH surge from releasing the eggs before they are collected. Prescribed by fertility specialists.
How does Ganirelix (Orgalutran) work?
What it does in the body, and where.Ganirelix blocks the pituitary signal that triggers ovulation, so eggs can ripen under IVF drugs without being released early.
- 01The triggerGnRH from the hypothalamus tells the pituitary to release LH and FSH. As follicles mature, a sudden LH surge sets off ovulation. In an IVF cycle that would release the eggs before they can be collected.
- 02Blocking the receptorGanirelix sits in the GnRH receptor without switching it on. LH falls within hours, and FSH to a lesser degree, with none of the initial burst of release seen with agonists such as leuprolide. Injected FSH keeps the follicles growing.
- 03Short and reversibleIts half-life is about 13 to 16 hours, so it is given daily only for the days it is needed, in the trials from day 6 of stimulation to the hCG trigger. LH and FSH recover fully within 48 hours of the last dose.
A schematic of the compound's mechanism, not a diagnostic image.
What else is it used for?
Each group carries its own evidence level.Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
Dose finding
FDA-approved- Human trial332 women, six doses from 62.5 to 2,000 mcg a day: 250 mcg gave the best results, with pregnancy in 35.7% per attempt (25 of 70), implantation 21.9% and an LH rise to 10 mIU/mL or more in 1 woman.
Against buserelin
FDA-approved- Human trial730 women: ongoing pregnancy 20.3% against 25.7% per attempt, implantation 15.7% against 21.8%, ovarian hyperstimulation 2.4% against 5.9%, with 5 days of treatment instead of 26.
Against leuprolide
FDA-approved- Human trial313 women: eggs per attempt 11.6 against 14.1, clinical pregnancy 35.4% against 38.4%, ongoing pregnancy 30.8% against 36.4%.
Against cetrorelix
peer-reviewed-human- Human observationSingle-center cohort in China, 7,059 ganirelix and 2,365 cetrorelix cycles after matching: live birth 49.4% against 47.2% (p=0.074) and clinical pregnancy 56.2% against 54.8%.
- Human observationLH of 10 U/L or more on trigger day was more common with ganirelix (7.6% against 4.9%, p<0.001); ovarian hyperstimulation was 1.1% against 0.4%, and the paper is inconsistent on whether that gap is significant.
Pregnancy outcomes
FDA-approved- Human observationFollow-up of more than 1,000 newborns found rates of birth defects comparable to historical controls treated with GnRH agonists.
- No dataThe label's pooled table lists fetal death in 3.7% (29 of 794); these are pregnancy losses in IVF cycles in a table with no comparison group, not a rate caused by the drug.
Antagon is often quoted as the US brand, but it was only the 1999 approval name; Organon now sells it as Ganirelix Acetate Injection. It is sometimes described as a generic of cetrorelix or the same drug: the two share most of their structure but differ at position 6 (diethyl-D-homoarginine against D-citrulline) and position 8 (diethyl-homoarginine against arginine), have separate NDAs, and ganirelix came first (July 29, 1999, against August 11, 2000). Fyremadel is reported as Ferring's own product; it is a Sun Pharma generic (ANDA 204246) that Ferring distributes. Half-lives of 13 and 16 hours are both right: 12.8 hours after one dose and 16.2 hours after repeated doses. The label's figure of under 1% for a premature LH surge and the 2.8% figure measure different things: a true surge, against any LH rise to 10 IU/L or more (13 of 463). The European trial's mean egg count is 8.7 in the label and 9.1 in the paper, probably on different denominators. The EMA gives May 17, 2000 for the EU authorization in one place and May 16 in another. The 3.7% fetal death line in the label's adverse event table counts pregnancy losses in IVF cycles in a pooled table with no comparison group; it is not a rate caused by the drug.
The published record
Papers and trials about Ganirelix (Orgalutran)
264 papers tagged human · 136 not reviews or lab · 62 clinical trial publications
105 registered trials · 16 with posted results
Furthest stage reached: Approved in the US
Counted from Europe PMC indexing, not read by a person; a human tag can land on reviews, commentary or lab papers; clinical trial publications is the narrower count. 217 papers and 100 trials indexed in detail.
At a glance
Four things to know about Ganirelix (Orgalutran)
Evidence
FDA-approved
Category
Sexual and hormonal
Common vial
Varies
Half-life
About 13 hours after one dose, 16 hours with daily dosing
How much, and do you cycle it?
The range, and whether you take breaks.250 mcg once a day during ovarian stimulation (label), once a day until the day of the hcg trigger shot. Daily for several days in each stimulation cycle FDA label
Given once a day from mid-stimulation until the hCG trigger (a median of 5 days in the European trial), then stopped.
How long does it stay in the body?
The half-life, and where the figure comes from.About 13 hours after one dose, 16 hours with daily dosingFDA label
Healthy women given 250 mcg under the skin: peak at about 1.1 hours, bioavailability 91.1%, steady state in 3 days, 81.9% protein-bound. After an intravenous dose, 75.1% was recovered in feces and 22.1% in urine. LH and FSH recover fully within 48 hours of stopping.
Source: Ganirelix Acetate Injection US prescribing information, Clinical Pharmacology (Pharmacokinetics)
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How is it given?
Dosing context and source notes.Supplied as a pen or prefilled syringe, so there is nothing to mix.
Label dose: 250 mcg per day. Ganirelix Acetate Injection US prescribing information (Organon, revised 2/2024), Dosage and Administration
250 mcg injected under the skin once a day, starting after FSH stimulation has begun (FSH from cycle day 2 or 3), in the mid to late follicular phase; in the trials it started on day 6 of FSH. It continues daily up to the day of the hCG trigger, and hCG is withheld if the ovaries are abnormally enlarged, to lower the risk of hyperstimulation. There is no titration: a dose-finding study of 62.5 to 2,000 mcg found the best pregnancy and implantation rates at 250 mcg. The EU label starts it on day 5 or 6 of FSH and says no more than 30 hours should pass between injections, or between the last injection and hCG. Kidney and liver impairment were not studied in the US label; the EU label rules it out in moderate or severe impairment. Supplied as a single-dose prefilled syringe of 250 mcg in 0.5 mL with a 27-gauge, half-inch needle attached, stored at room temperature, so there is nothing to mix.
How do you store it?
Before mixing, and after.Supplied ready to use. Store it as the label says.
Ganirelix (Orgalutran) comes as a ready-made solution, prefilled syringe or ampoule, not a powder, so there is no mixing step and no reconstitution clock. Keep it in its original pack and follow the storage and expiry dates on the label. Many ready-made peptide medicines are kept in the fridge and must not be frozen; a few are made to be stored at room temperature.
What are the side effects and cautions?
Known cautions and warnings for this compound.Solubility, computed: 40% charged residues, 60% hydrophobic. Water usually sufficient.
A first-pass rule from peptide manufacturers' guidance. It does not account for disulfide bridges, salt form or how the powder was dried, and it predicts what should be easy rather than what will happen in your vial.
Who should avoid it
- Allergy to ganirelix or any ingredient, including the natural rubber latex needle shield on some syringes
- Allergy to GnRH or any GnRH analog
- Known or suspected pregnancy; breastfeeding is also ruled out (EU label) or advised against (US label)
- Moderate or severe kidney or liver impairment (EU label)
Stop and get help
- Hives, swelling of the face or throat, or trouble breathing: possible anaphylaxis, reported as early as the first dose
- Any allergic reaction in someone with a latex allergy, as some needle shields contain natural rubber latex
Common effects
- Gynecological abdominal pain 4.8%, headache 3.0%, vaginal bleeding 1.8% and nausea 1.1% in the label's pooled data (794 women, no comparison group)
- Moderate injection-site reactions in 11.9% against 24.4% with leuprolide (North American trial); the EU label lists redness at the injection site, with or without swelling, as very common
- Ovarian hyperstimulation syndrome in 2.4% against 5.9% with buserelin (European trial)
- Neutrophil counts of 8.3 billion per liter or higher in 11.9%, with small falls in hematocrit and bilirubin
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Ganirelix (Orgalutran) approved?
And where the numbers on this page come from.Yes. Ganirelix (Orgalutran) is FDA approved and available on prescription in the United States. It is also approved in the European Union, Australia, and Japan.
- Approval statusFDA-approved
- RouteUnder the skin (prefilled syringe)
- Checked16 October 2026
- Approved outside the USEuropean Union, Australia, Japan: EU authorization of Orgalutran (Organon N.V.) on May 17, 2000, and of the generic Ganirelix Gedeon Richter on July 15, 2022; registered in Australia on March 19, 2001; sold in Japan as Ganirest (approval date not established). Also FDA-approved in the US since July 29, 1999.This does not change the United States position above.
- DoseFrom the drug label. The manufacturer tested this range and a regulator reviewed it.
- Vial sizeFrom what vendors typically list; not a recommendation.
- SourcesDrugs@FDA, NDA 021057FDA approval letter, Antagon (1999)DailyMed, Ganirelix Acetate Injection (Organon)openFDA drugsfda, ganirelix acetateopenFDA drugsfda, cetrorelix acetateFDA GSRS substance record, ganirelix (UNII IX503L9WN0)EMA, Orgalutran EPAROrgalutran EU summary of product characteristicsEMA, Ganirelix Gedeon Richter EPAREuropean Orgalutran Study Group (Borm G, Mannaerts B), Human Reproduction 2000;15:1490-1498Fluker M et al., Fertility and Sterility 2001;75:38-45PBAC public summary document, ganirelix (2009)Peng X et al., Frontiers in Reproductive Health 2025;7:1492441DailyMed, Fyremadel
What has happened recently
The FDA approved ganirelix on July 29, 1999 (NDA 021057, Organon, a new molecular entity with priority review) as Antagon, making it the first GnRH antagonist approved in the US, ahead of cetrorelix (Cetrotide) on August 11, 2000. Organon's product is now labeled Ganirelix Acetate Injection and is the reference drug for seven US generics: Fyremadel (made by Sun Pharma, distributed by Ferring, November 30, 2018), then Amphastar, Meitheal, Gland, Lupin, Qilu and Tris Pharma between April 7, 2022 and June 27, 2025; the Tris Pharma version is discontinued. In the EU, Orgalutran (Organon N.V.) was authorized on May 17, 2000, and the generic Ganirelix Gedeon Richter on July 15, 2022. Australia registered it on March 19, 2001, and Japan sells it as Ganirest.
You can compare this against the whole library, or read how to check a seller.
What else is like Ganirelix (Orgalutran)?
Others in Sexual and hormonal, side by side.If you're weighing Ganirelix (Orgalutran), it's worth reading Goserelin (Zoladex), Lanreotide (Somatuline Depot), and Leuprolide (Lupron) in the same class.
A ten-residue GnRH blocker injected once a day during IVF stimulation to prevent an early LH surge. FDA-approved since July 29, 1999, with seven US generic approvals since 2018.
- Dose
- 250 mcg once a day during ovarian stimulation (label)
- How often
- Once a day until the day of the hCG trigger shot
A GnRH agonist given as an implant under the skin rather than an injection.
- Dose
- Set by the label
- How often
- Monthly or 3-monthly implant
An approved monthly somatostatin shot that lowers growth hormone and slows some gut and pancreatic tumors.
- Dose
- 60 to 120 mg every 4 weeks (label)
- How often
- Every 4 weeks (6 to 8 weeks for some acromegaly patients)
The GnRH agonist that shuts hormones down by overstimulating them first.
- Dose
- Set by the label and the depot formulation
- How often
- Monthly to six-monthly depot
Guides for this compound
- How to Reconstitute a Peptide
Mix peptide powder with bacteriostatic water, step by step.
- How to Read an Insulin Syringe
Read the units, convert to millilitres, and draw the exact dose.
- mcg vs mg: The Peptide Dosing Mistake to Avoid
Your vial says mg and your protocol says mcg. Here is the conversion and how to check it.
Sources
- Drugs@FDA, NDA 021057(2024)Approved July 29, 1999 as a new molecular entity with priority review; Organon; supplement history through 2024.
- FDA approval letter, Antagon (1999)(1999)Approved to Organon, Inc. as Antagon 250 mcg/0.5 mL for inhibiting premature LH surges in women undergoing controlled ovarian hyperstimulation.
- DailyMed, Ganirelix Acetate Injection (Organon)(2025)Chemical name, dose and supply; half-life 12.8 hours after one dose and 16.2 hours after repeated doses; pooled adverse events in 794 women; dose-finding and European trials.
- openFDA drugsfda, ganirelix acetate(2026)One NDA (1999) and seven ANDAs, the ANDAs approved from November 30, 2018 to June 27, 2025.
- openFDA drugsfda, cetrorelix acetate(2026)Cetrotide, NDA 021197, approved August 11, 2000, after ganirelix.
- FDA GSRS substance record, ganirelix (UNII IX503L9WN0)(2026)C80H113ClN18O13, MW 1570.3; CAS 124904-93-4; ten defined stereocenters; ATC H01CC01.
- EMA, Orgalutran EPAR(2025)EU authorization May 17, 2000; Organon N.V., Oss, Netherlands.
- Orgalutran EU summary of product characteristics(2025)Start on day 5 or 6 of FSH; no more than 30 hours between injections; ruled out in moderate or severe kidney or liver impairment; half-life about 13 hours.
- EMA, Ganirelix Gedeon Richter EPAR(2022)EU generic of Orgalutran, authorized July 15, 2022.
- European Orgalutran Study Group (Borm G, Mannaerts B), Human Reproduction 2000;15:1490-1498(2000)730 women randomized 2:1 against buserelin: ongoing pregnancy 20.3% against 25.7%; ovarian hyperstimulation 2.4% against 5.9%; median treatment 5 against 26 days.
- Fluker M et al., Fertility and Sterility 2001;75:38-45(2001)313 women against leuprolide: ongoing pregnancy 30.8% against 36.4%; moderate injection-site reactions 11.9% against 24.4%.
- PBAC public summary document, ganirelix (2009)(2009)Registered in Australia March 19, 2001; Rombauts 2006 comparison with nafarelin.
- Peng X et al., Frontiers in Reproductive Health 2025;7:1492441(2025)Retrospective cohort, 7,059 ganirelix and 2,365 cetrorelix cycles after matching: live birth 49.4% against 47.2% (p=0.074); LH of 10 U/L or more on trigger day 7.6% against 4.9%.
- DailyMed, Fyremadel(2025)ANDA 204246, made by Sun Pharma and distributed by Ferring.
Beyond these, 317 records are indexed. Browse the records