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Ganirelix: quick citable summary
Ganirelix is listed by PeptaHub as a other peptide with a prescription legal-status classification. The page summarizes mechanism, research context, common routes, safety notes, and references for writers and AI answer engines.
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What is Ganirelix?
Ganirelix (Antagon/Orgalutran) is an FDA-approved synthetic decapeptide GnRH antagonist for IVF. It rapidly suppresses LH without a flare effect, resulting in shorter analogue treatment (median 5 days vs 26) and lower total FSH requirements than a GnRH agonist long protocol.
Overview
Ganirelix is a synthetic decapeptide GnRH antagonist used in assisted reproductive technology to prevent premature LH surges and unintended ovulation during controlled ovarian hyperstimulation for IVF. Originally sold in the US as Antagon and in Europe as Orgalutran, it is now marketed in the US as generic ganirelix acetate injection and as Fyremadel. It gives rapid pituitary suppression without the flare effect associated with GnRH agonists, which shortens the analogue treatment period and produced fewer moderate injection site reactions than leuprolide in its Phase III trial.
Mechanism of action
Ganirelix competitively occupies pituitary GnRH receptors, rapidly suppressing LH and FSH secretion. Amino acid substitutions at positions 1, 2, 3, 6, 8, and 10 of the native GnRH decapeptide provide metabolic stability and sustained receptor occupancy. Unlike GnRH agonists, ganirelix does not trigger receptor downregulation or an initial gonadotropin flare; suppression is immediate and reversible on discontinuation. Labeled pharmacokinetics give an absolute bioavailability of 91.1%, peak concentration about 1 hour after injection, a terminal half-life of 12.8 hours after a single dose and 16.2 hours with repeated dosing, and steady state after 3 days of daily administration.
Reported study ranges
| Purpose | Route | Reported range | Frequency | Notes |
|---|---|---|---|---|
| IVF — prevention of premature LH surge | subcutaneous | 0.25–0.25 mg | once daily | US labeling: 250 mcg subcutaneously once daily, started on day 6 or 7 of the follicular phase after FSH is begun on day 2 or 3, and continued daily until the day of hCG administration. Flexible-start protocols keyed to lead follicle size are used in practice but are not the labeled schedule. Administer at the same time each day. |
Reported ranges are for research context only. Consult a qualified healthcare professional before using any peptide.
Convert Ganirelix research-range units
Need to convert mg to mcg, dose volume, or U-100 syringe units? The Ganirelix dose calculator is preloaded with these ranges, or use the general dose unit converter.
Research summary
Dose-finding work established 0.25 mg daily as the dose carried into Phase III. The North American Phase III trial (Fluker et al., Fertil Steril 2001, n=313) compared ganirelix with a leuprolide long protocol: clinical pregnancy rates were 35.4% versus 38.4% and ongoing pregnancy 30.8% versus 36.4%, with fewer oocytes retrieved on ganirelix (11.6 vs 14.1) but fewer moderate injection site reactions (11.9% vs 24.4%). The authors concluded pregnancy rates were similar; the numerically lower ongoing pregnancy rate is worth noting since the trial was not powered to demonstrate equivalence on that endpoint. The European Orgalutran trial (Borm & Mannaerts, Hum Reprod 2000, n=730) was a non-inferiority study against a buserelin long protocol and showed the practical advantage clearly: median GnRH analogue treatment of 5 days versus 26, and median total recombinant FSH of 1,500 IU versus 1,800 IU. Prospective follow-up of 1,000 fetuses conceived after ganirelix (Bonduelle et al., Hum Reprod 2010) found no safety signal, though without a randomized comparator.[1][2][3][4][5][6]
Evidence grading
Each claimed benefit is graded by the strength of available evidence. Grades reflect study quality, not effect size.
Strong = multiple RCTs · Moderate = limited trials or observational · Preliminary = animal or in vitro only · Insufficient = anecdotal or no published data
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with Ganirelix for synergistic effects.
Legal status
FDA-approved (NDA 021057) for inhibition of premature LH surges in women undergoing controlled ovarian stimulation. Prescription-only; administered under reproductive endocrinologist supervision. EMA-approved as Orgalutran.
Sourcing & access
Prescription required
Ganirelix is an FDA-approved prescription medication available through licensed healthcare providers, pharmacies, and label-appropriate access programs; compounded access depends on current FDA shortage status and compounding rules.
Frequently asked questions
Ganirelix is a synthetic decapeptide GnRH antagonist used in IVF to prevent premature luteinizing hormone surges and unintended ovulation during controlled ovarian stimulation. It is FDA-approved and sold as Antagon in the United States and Orgalutran in Europe. Multiple D-amino acid substitutions confer higher binding affinity than native GnRH and enable rapid, reversible pituitary suppression without an initial flare.
Both are GnRH antagonists used for the same purpose in IVF. Ganirelix has a longer terminal half-life (12.8 hours after a single dose, per its label) than cetrorelix at the 0.25 mg dose. Published comparisons have not shown a consistent difference in clinical outcomes between the two.
US labeling directs that ganirelix 250 mcg be started on day 6 or 7 of the follicular phase, with FSH begun on day 2 or 3, and continued daily until the day of hCG administration. Many clinics instead use a flexible start keyed to lead follicle size; that is common practice rather than labeled dosing.
Common side effects include injection site reactions such as bruising, redness, and swelling, along with abdominal pain, headache, nausea, and vaginal bleeding. In the North American Phase III trial, moderate injection site reactions were less frequent with ganirelix than with leuprolide (11.9 versus 24.4 percent). Ovarian hyperstimulation syndrome remains a risk of controlled ovarian stimulation generally. Ganirelix is contraindicated in known or suspected pregnancy, in known hypersensitivity to GnRH or any GnRH analog, and in hypersensitivity to the product or its components, which include dry natural rubber or latex in some presentations.
Research references
- Large prospective, pregnancy and infant follow-up trial assures the health of 1000 fetuses conceived after treatment with the GnRH antagonist ganirelix during controlled ovarian stimulationPubMed
- Efficacy and safety of ganirelix acetate versus leuprolide acetate in women undergoing controlled ovarian hyperstimulationPubMed
- Treatment with the gonadotrophin-releasing hormone antagonist ganirelix in women undergoing ovarian stimulation with recombinant follicle stimulating hormone is effective, safe and convenient: results of a controlled, randomized, multicentre trial (European Orgalutran Study Group)PubMed
- Obstetrical and neonatal outcome after controlled ovarian stimulation for IVF using the GnRH antagonist ganirelixPubMed
- Treatment with the GnRH antagonist ganirelix prevents premature LH rises and luteinization in stimulated intrauterine insemination: results of a double-blind, placebo-controlled, multicentre trialPubMed
- Efficacy and safety of newly developed ganirelix acetate in infertile women for assisted reproductive technology: a prospective, randomised, controlled studyPubMed