Antagon (ganirelix acetate)
Antagon produces the same biologic effects as Lupron by a different mechanism. Lupron is a GnRH agonist whereas Antagon is a GnRH antagonist, which immediately stops the production of gonadotropin releasing hormone (GnRH). It blocks the action of GnRH at the pituitary gland and causes a much quicker and complete suppression of GnRH levels. This leads to an effective blocking of the LH surge, thereby preventing the premature release of the eggs.
Because the suppression is so complete, higher dosages of FSH may be required during the time the patient is receiving Antagon. However, Antagon cycles typically require less total FSH than corresponding Lupron cycles. We prefer Antagon due to fewer injections, less FSH, and a much simpler protocol. Lupron (leuprolide acetate).
Lupron (leuprolide acetate) was originally introduced for the treatment of endometriosis. It is a GnRH agonist which means that it temporarily depletes the body of FSH and LH. GnRH stimulates the pituitary to release FSH and LH thus leading to lower levels of FSH, LH, and estrogen (through the hypothalamic pituitary feedback mechanism). Lupron is effective in treating endometriosis because it lowers estrogen levels upon which endometrial cells depend.
Lupron is administered during IVF cycles according to specific treatment protocols dependent upon patient specific variables. Therapy usually begins 7 days prior to the next expected menses. Lupron effectively blocks the production of the reproductive hormones FSH and LH. The specialist administers exogenous FSH, closely monitors the development of the follicles, and adjusts the dosage accordingly.
Ovulation cannot occur while taking Lupron unless an injection of hCG is given. This is extremely important since ovulation must be carefully timed with egg retrieval or the IVF cycle could be “lost”. Lupron enables the specialist to control most of the endocrine events occurring during the cycle.
The most significant side effects of Lupron are menopausal symptoms. Side effects are more common with extended therapy.