FDA Approved Sexual & Reproductive Health

Ganirelix

also known as: Ganirelix Acetate, Orgalutran, Antagon

Organon/Merck's Ganirelix Acetate (formerly Antagon; Orgalutran internationally) — a GnRH antagonist functionally equivalent to cetrorelix for IVF LH-surge prevention, dosed as a daily fixed 250 mcg SC injection.

A synthetic decapeptide GnRH-receptor antagonist structurally related to cetrorelix and developed in parallel by Organon. FDA-approved in 1999 as Antagon, now marketed generically as Ganirelix Acetate Injection. Used in the same clinical role as cetrorelix — blocking premature LH surges during IVF controlled ovarian stimulation — with a simpler fixed single-dose regimen of 250 mcg daily.

Mechanism of action

Immediate competitive blockade of pituitary GnRH receptors, suppressing LH and FSH secretion without initial flare. Daily 250 mcg SC dose provides sustained LH-surge prevention until hCG trigger.

Primary uses

  • Prevention of premature LH surge during IVF controlled ovarian stimulation

Typical dosing

250 mcg daily (subcutaneous (thigh or abdomen))

Initiated on stimulation day 5 or 6 when adequate follicular development is present, or when estradiol rises rapidly. Continued daily through day of hCG administration.

Regulatory status

FDA-approved as Antagon (ganirelix acetate, Organon, approved 1999) for inhibition of premature LH surges in women undergoing controlled ovarian hyperstimulation. Branded Antagon was discontinued in the US but the drug remains available as generic Ganirelix Acetate Injection (Organon / Merck and others). Marketed internationally as Orgalutran.

References

  1. [fda-pi] Ganirelix Acetate Injection Prescribing Information. Organon USA.
  2. [pubmed] European Orgalutran Study Group. "Treatment with the gonadotrophin-releasing hormone antagonist ganirelix in women undergoing ovarian stimulation with recombinant follicle stimulating hormone is effective, safe and convenient." Hum Reprod, 2000;15:1490-1498.

Related peptides

Cetrorelix

Merck Serono's Cetrotide — a GnRH antagonist used during IVF controlled ovarian stimulation to block premature LH surges. Unlike GnRH agonists, produces immediate gonadotropin suppression without a flare, shortening IVF cycles.

Degarelix

Ferring's Firmagon — a GnRH antagonist for advanced prostate cancer that achieves castrate testosterone within 3 days, eliminating the clinical flare risk of GnRH-agonist therapy in patients with symptomatic bone metastases or impending spinal cord compression.

Gonadorelin

The native GnRH decapeptide — the hypothalamic signal that drives LH/FSH release and downstream testosterone/estradiol production. Historically FDA-approved (Factrel, Lutrepulse), now widely used in TRT-adjacent fertility protocols as a testicular-preservation alternative to HCG.

Follitropin alfa

EMD Serono's Gonal-f — the first recombinant human FSH approved by the FDA (1997). Used for ovulation induction, IVF controlled ovarian stimulation, and male hypogonadotropic hypogonadism fertility induction.

HCG

An FDA-approved fertility and hypogonadism medication commonly discussed in peptide and TRT communities for post-cycle recovery and testicular preservation during testosterone therapy.
Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.