Notes: Ganirelix is a gonadotropin-releasing hormone receptor (GNRHR) antagonist (IC50 = 3.6 nM; pA2 = 9.3).{39553} It induces a concentration-dependent increase in histamine release from rat peritoneal mast cells in vitro (EC50 = 11 μg/ml).{40810} In vivo, ganirelix (2 mg/kg, s.c.) decreases plasma testosterone in intact male rats for the first 7 days post-administration. Ganirelix (125 μg per day for 30 days) decreases the surface area of endometriotic lesions and serum progesterone levels in female baboons.{40811} Formulations containing ganirelix have been used to prevent premature ovulation in women undergoing in vitro fertilization.