Lupron (leuprolide acetate), Antagon (ganirelix acetate), Cetrotide (cetrorelix acetate)

Lupron, Antagon, and Cetrotide are fertility drugs that "down regulate" reproductive hormone production causing a reduction in levels of follicle stimulating hormone, luteinizing hormone, and estrogen. Lupron, Antagon, and Cetrotide all cause these effects, however, by different physiologic mechanisms.

Lupron is widely used for the treatment of endometriosis and was the first "down regulator" used in in vitro fertilization cycles. Endometrial cells are dependent upon estrogen for growth and Lupron dramatically lowers estrogen levels. Unfortunately, this lowering is accompanied by the same side effects as menopause.

Lupron, Antagon and Cetrotide are administered according to specific protocols in IVF to prevent premature ovulation, and in some cases to exacerbate the response to follicle stimulating hormone (flare protocol).

Lupron is a GnRH agonist which works at the hypothalamus (a small gland located at the base of the brain ) whereas Antagon is a GnRH antagonist which completely blocks the effect of gonadotropin releasing hormone at the pituitary gland thus creating a "more complete "down regulation".

IVF cycles are precisely timed to insure that the follicles are optimally developed at the time of retrieval. FSH is administered and dosages are adjusted based upon periodic ultrasound scans and estradiol measurements. In a "normal" or "non-stimulated" cycle, luteinizing hormone surges to signal ovulation.

If this occurs too soon in an IVF cycle, ovulation could be triggered before the eggs are mature and the cycle could be lost. The LH surge cannot occur while Lupron, Antagon, or Cetrotide are administered thus premature ovulation is prevented.

Once the follicles are mature, an injection of hCG is given 36-38 hours prior to retrieval to signal ovulation. The body responds to hCG in the same manner as it does to LH.

Many infertility clinics choose to use Antagon or Cetrotide because the down regulation is more complete and the dosing regimen is easier. Lupron is started 7 days before the next expected menses and Antagon or Cetrotide is started after 4 to 6 days of FSH stimulation. Doses vary dependent upon patient specific protocols.

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