Antagon (Ganirelix Acetate Injection) belong to a class of drugs known generically as Ganirelix, which is a gonadotropin-releasing hormone (GnRH) used by fertility doctors to prevent premature luteinizing hormone (LH) surges in women undergoing controlled ovarian hyperstimulation during the fertility process. Antagon helps reduce the need for follicle-stimulating hormones (FSH) typically used to maximize the success rates in vitro fertilization, by harvesting a sufficient number of eggs from the woman (about 8-15 high-quality eggs at the egg retrieval procedure).
Other drugs that are also used to prevent LH surge and premature egg release include Cetrotide (cetrorelix acetate) and Lupron (leuprolide acetate). A positive aspect of Antagon is that it results in a less shots being taken than using Lupron, but some studies have shown that there are slightly fewer eggs retrieved (on average). However, though this may be the case, pregnancy rates are still excellent with Antagon, when used properly in selected patients. Some clinics even report that Antagon may be better for women who are low responders to Lupron, during ovarian stimulation protocols.
How Antagon Works
Antagon, like all other Ganirelix medications, is a gonadotropin-releasing hormone (GnGH) antagonist, thus stopping something in your body from working. These medications stop the eggs from being released before a woman’s body triggers the release by starting hCG by blocking the action of GnRH by competing with them and binding sites in the pituitary.
How Antagon is Used
Fertility doctors start by looking at your history, and may first have the woman take a birth control pill for three to five weeks prior. In this way, the woman’s ovaries will allow to “rest,” increasing the doctor’s ability to control the response to the medication. Near the end of the birth control pill packet, the IVF coordinator will then schedule to evaluate whether the woman’s ovaries are suppressed, to then begin taking active stimulation medications (Bravelle, Follistim, Gonal F., Menopur Reponex).
The woman will begin Antagon, in conjunction with Cetrotiden, when her blood level and follicles have reached an appropriate size. Antagon is usually started on (about) the sixth day of administering the FSG product which stimulates the development of follicles in the ovaries. Antagon is given subcutaneously once a day until HCG is given.
