Tuesday 13 November 2007

Medications for Down Regulation

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

Lupride 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 Lupride dramatically lowers estrogen levels. Unfortunately, this lowering is accompanied by the same side effects as menopause. Lupride and Ovurelix 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).

Lupride is a GnRH agonist which works at the hypothalamus (a small gland located at the base of the brain ) whereas Ovurelix 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 Lupride or Ovurelix are administered and 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 Lupride or Ovurelix because the down regulation is more complete and the dosing regimen is easier. Lupride is started 7 days before the next expected menses and Ovurelix is started after 4 to 6 days of FSH/hMG stimulation. Doses vary dependent upon patient specific protocols.

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