Ganirelix (Fyremadel)

Summary

Ganirelix is an FDA approved GnRH antagonist (approved 1999), a drug that blocks the brain hormone signal that triggers ovulation, given as a 250 mcg daily injection under the skin during ovarian stimulation for IVF to prevent a premature LH surge (the hormone spike that releases eggs). A Cochrane review (a rigorous pooled analysis) of 73 randomized trials in 12,212 women found no difference in live birth rate between antagonist and the older long agonist protocols (odds ratio 1.02, essentially equal) and a roughly 40% lower rate of ovarian hyperstimulation syndrome, a dangerous overreaction of the ovaries, with antagonists. It is a routine fertility clinic drug, not a research peptide.

What is Ganirelix?

Ganirelix is a gonadotropin releasing hormone (GnRH) antagonist, synthetic decapeptide. It is also known as Ganirelix Acetate Injection, Orgalutran, Antagon, Fyremadel, Org 37462.

How does it work?

Ganirelix competitively blocks GnRH receptors on pituitary gonadotroph cells. Within hours it suppresses release of LH and, to a lesser extent, FSH, without the initial flare of hormone release that GnRH agonists cause. Starting it midway through ovarian stimulation prevents the premature LH surge that would otherwise trigger ovulation before egg retrieval, and suppression reverses within about 2 days of stopping.

FDA-approved uses of Ganirelix

Yes, since 1999, sold today as ganirelix acetate injection and Fyremadel along with several generics. The label has one use: inhibiting premature LH surges (the hormone spike that triggers ovulation) in women undergoing controlled ovarian hyperstimulation for assisted reproduction. It blocks pituitary GnRH receptors, the switch the brain uses to release LH, so that ovulation can be triggered on schedule with an hCG shot. [5] [7]

What does the evidence say about Ganirelix?

Multiple randomized trials and a large Cochrane meta-analysis. A dose finding trial (n = 333) established 0.25 mg daily as the optimal dose. Randomized comparisons against long agonist protocols (triptorelin, n = 730; leuprolide, n = 313) showed shorter stimulation, fewer gonadotropin doses, and similar although numerically slightly lower ongoing pregnancy rates. Cochrane 2016 (73 RCTs, 12,212 women): live birth odds ratio 1.02 (95% CI 0.85 to 1.23) and ovarian hyperstimulation syndrome odds ratio 0.61 (95% CI 0.51 to 0.72) for antagonists versus agonists.

Human evidence

Ganirelix Dose-finding Study Group 1998 (n = 333, six doses from 0.0625 to 2 mg daily): 0.25 mg gave the highest implantation and ongoing pregnancy rates, with higher doses suppressing LH too deeply. European and Middle East Orgalutran Study Group 2001 (n = 730): ongoing pregnancy rate 20.3% with ganirelix versus 25.7% with a long triptorelin protocol, with 5 fewer days of gonadotropins and no premature LH surges in either arm at meaningful rates. Fluker 2001 (n = 313, North America): ganirelix versus leuprolide, comparable safety and pregnancy outcomes with a shorter treatment course. Cochrane 2016 pooled across all GnRH antagonists: no difference in live birth, 39% lower odds of OHSS.

Animal evidence

Preclinical studies in rats and monkeys established rapid, reversible suppression of LH and FSH and set the dose range. Reproductive toxicology showed fetal resorption when given during early pregnancy, which underlies the pregnancy contraindication.

Key studies

Conditions studied

Is Ganirelix legal in the United States?

FDA and compounding status

FDA approved prescription drug (originally Antagon, approved July 1999; now sold as Ganirelix Acetate Injection and generic and branded equivalents). Commercially available in prefilled syringes, so it is not eligible for routine compounding and is not on any 503A bulks list. Not a research chemical.

WADA status

Not WADA prohibited. Not named on the current prohibited list. Athletes should still confirm against the list in force for their season.

Regulatory timeline

No regulatory events recorded.

Full tracker for Ganirelix or the category-wide tracker.

Ganirelix dose on the FDA label

Doses below are quoted from the FDA label for its approved uses, plus the doses used in the pivotal trials where noted. The prescriber sets the dose; PeptideAgent does not recommend doses or protocols.

FDA label (ganirelix acetate injection, DailyMed): after FSH therapy starts on cycle day 2 or 3, 250 mcg is injected subcutaneously once daily during the mid to late portion of the follicular phase and continued daily until the day of hCG administration. The label says hCG should be withheld if the ovaries are abnormally enlarged on the last day of FSH therapy, to lower the chance of ovarian hyperstimulation syndrome. The dose finding trial tested 0.0625 to 2 mg daily and selected 0.25 mg.

Routes reported

What are the side effects and interactions of Ganirelix?

Side effects

Interactions

Contraindications

How do people access Ganirelix legally?

Typical cost: Roughly 100 to 200 USD per 250 mcg prefilled syringe at US pharmacies, and a typical IVF cycle uses 4 to 6 syringes. Fertility benefits vary widely; many patients pay cash as part of an IVF medication package. Prices verified on the last verified date.

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Frequently asked questions

Decisions about starting, stopping, or combining any treatment belong with a licensed clinician who knows your history.

Sources

Numbered citations above point to these primary sources. PubMed entries link to the indexed abstract.