Ganirelix

Overview

Ganirelix is a lab-made peptide that briefly blocks the brain signal that triggers ovulation. Fertility clinics use it as a daily injection during IVF so that eggs are not released before they can be collected. It was the first drug of its kind approved in the US (1999), and several generic versions have since been approved.

How it works

Established: ganirelix competitively blocks GnRH receptors on the pituitary gland, quickly and reversibly lowering release of LH and, to a lesser degree, FSH ¹. No initial hormone surge is seen, unlike with GnRH agonists, and LH and FSH return to normal within 48 hours after stopping ¹. During IVF stimulation this prevents a premature LH surge, which would otherwise trigger ovulation before egg retrieval ¹.

What research shows

• Dose-finding RCT (double-blind, n=332 treated with 62.5 to 2000 mcg daily): LH suppression increased with dose, and the 250 mcg dose gave the highest pregnancy rate (35.7% per attempt) and implantation rate (21.9%) ¹.
• Phase 3 open-label RCT (n=463 on ganirelix 250 mcg, compared with a long GnRH agonist protocol): a true premature LH surge occurred in under 1% of women; ongoing pregnancy rate was 20.3% per attempt ¹. In a review by an Organon author, the first Phase 3 trial (about 700 women, 2:1 vs a long buserelin protocol) showed a −5.4% difference in ongoing pregnancy that was not statistically significant ⁴.
• Head-to-head RCT vs cetrorelix (CAP IV, open-label, n=185): no premature LH surge in either group and no significant difference in pregnancy or other IVF outcomes ⁶.
• Cochrane review (73 RCTs, n=12,212) of GnRH antagonists as a class vs long agonist protocols: no clear difference in live birth (OR 1.02), with less ovarian hyperstimulation syndrome on antagonists (OR 0.61); evidence quality moderate ⁵.
• Placebo-controlled RCT in stimulated intrauterine insemination (n=203): premature LH rises in 3.9% on ganirelix vs 28.0% on placebo, with similar ongoing pregnancy rates (12.6% vs 12.0%) ¹².

Doses studied in people

Doses shown are from the FDA label and published trials only; they are reported, not recommended. Ganirelix is used only under a fertility specialist's care.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Safety

• Label adverse events (n=794 in controlled trials, from first dose to pregnancy confirmation, regardless of cause): gynecological abdominal pain 4.8%, fetal death 3.7%, headache 3.0%, ovarian hyperstimulation syndrome 2.4%, vaginal bleeding 1.8%, injection-site reaction 1.1%, nausea 1.1% ¹.
• Rare allergic reactions, including anaphylaxis, angioedema and hives, have been reported after marketing, sometimes with the first dose ¹.
• One presentation has a needle shield that may contain natural rubber latex; latex allergy is listed as a contraindication ¹.
• A raised neutrophil count was seen in 11.9% of trial participants, with small drops in hematocrit and bilirubin; clinical meaning unknown ¹.
• Contraindicated in known or suspected pregnancy; in animals it increased pregnancy loss (litter resorption). Not to be used while breastfeeding ¹.
• Birth defects: the current label cites an observational study of more than 1,000 newborns in which congenital anomaly rates after ganirelix were similar to those after a GnRH agonist protocol; it notes that IVF/ICSI itself may slightly raise these rates and that any causal link to ganirelix is unknown ¹.
• No long-term animal cancer studies have been done ¹.

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Legal status

FDA

FDA-approved (NDA 021057, July 29, 1999; now Organon USA) to inhibit premature LH surges in women undergoing controlled ovarian hyperstimulation; a current prescription product ¹². Generic ganirelix 250 mcg/0.5 mL is approved from several companies, starting with Sun Pharma's Fyremadel (November 2018), followed by Amphastar, Meitheal, Gland, Lupin and Qilu; one (Tris Pharma) is listed as discontinued ³.

Compounding

Not named in FDA's 503A nominated bulk substances category list (updated May 14, 2026) ¹⁰. FDA-approved brand and generic products exist.

Sports (WADA)

Not named on the WADA 2026 Prohibited List. Section S2.2.1 bans GnRH and its agonist analogues in males; antagonists such as ganirelix are not listed ⁸.

Other

Prescription-only (Rx only) ¹. Authorized in the EU as Orgalutran (Organon) since May 2000 ⁷.

Rules change often. See Legal status of peptides for how these categories work.

Storage and stability

Label: store at 25°C (77°F), excursions 15–30°C allowed; protect from light ¹.

General lab handling, not instructions for personal use. See Storage and stability.

History

Ganirelix was first made and studied by Syntex Research in Palo Alto (as RS-26306), initially with long-term treatment of hormone-dependent diseases such as prostate cancer in mind ⁴. Organon then developed it (as Org 37462) for preventing premature LH surges in assisted reproduction ⁴. The FDA approved it on July 29, 1999 after a priority review, making it the first GnRH antagonist approved in the US ²⁴. The EU authorized it as Orgalutran in May 2000 ⁷. The original US product is now held by Organon USA, and several generic versions have been approved since 2018, starting with Sun Pharma's Fyremadel ²³.

Common questions

Related compounds

Sources

1. Ganirelix Acetate Injection Prescribing Information (Organon), revised 9/2024 (FDA) FDA label
2. Drugs@FDA: Ganirelix Acetate, NDA 021057 (Organon USA; approval date, marketing status) Regulatory
3. openFDA Drugs@FDA query: products containing ganirelix (NDA and ANDA marketing status) Regulatory
4. Mannaerts B. Ganirelix and the prevention of premature luteinizing hormone surges. F&S Reports 2023 (author employed by Organon) Journal
5. Al-Inany HG et al. Gonadotrophin-releasing hormone antagonists for assisted reproductive technology. Cochrane Database Syst Rev 2016 (PMID 27126581) PubMed review
6. Wilcox J et al. Prospective, randomized trial comparing cetrorelix acetate and ganirelix acetate in a programmed, flexible protocol. Fertil Steril 2005 (PMID 16009165) Journal
7. EMA: Orgalutran EPAR (EU authorisation details) Regulatory
8. WADA Prohibited List 2026, full text (Asia Rugby copy) Regulatory
9. PubChem: Ganirelix (CID 16130957) computed properties Regulatory
10. FDA: Bulk Drug Substances Nominated for Use in Compounding Under Section 503A (updated May 14, 2026) Regulatory
11. PubChem: Ganirelix (CID 16130957) CAS registry number Regulatory
12. Lambalk CB et al. Ganirelix prevents premature LH rises and luteinization in stimulated intrauterine insemination: double-blind, placebo-controlled trial. Hum Reprod 2006 (PMID 16361296) Journal