Ganirelix acts by competitively blocking the GnRH receptors on the pituitary gonadotroph and subsequent transduction pathway. It induces a rapid, reversible suppression of gonadotropin secretion. The suppression of pituitary LH secretion by ganirelix is more pronounced than that of FSH. An initial release of endogenous gonadotropins has not been detected with ganirelix, which is consistent with an antagonist effect. Upon discontinuation of ganirelix, pituitary LH and FSH levels are fully recovered within 48 hours.

Following single-dose intravenous administration of radiolabeled ganirelix acetate to healthy female volunteers, ganirelix Acetate is the major compound present in the plasma (50–70% of total radioactivity in the plasma) up to 4 hours and urine (17.1–18.4% of administered dose) up to 24 hours. Ganirelix Acetate is not found in the feces. The 1–4 peptide and 1–6 peptide of Ganirelix Acetate are the primary metabolites observed in the feces.

Oberye J, Mannaerts B, Huisman J, Timmer C: Local tolerance, pharmacokinetics, and dynamics of ganirelix (Orgalutran) administration by Medi-Jector compared to conventional needle injections. Hum Reprod. 2000 Feb;15(2):245-9. Pubmed