Cetrorelix is a luteinizing hormone releasing hormone (LHRH) antagonist used in combination with other hormones during controlled ovarian stimulation in assisted reproduction, such as in vitro fertilization (IVF). It is normally given by sub-cutaneous injection, that is just beneath the skin. The process of controlled ovarian stimulation should be conducted under the medical supervision of a fertility specialist.
There are five main hormones involved a women’s fertility and menstrual cycle which work together, surging at specific times. They are follicle-stimulating hormone (FSH), gonadotropin-releasing hormone (GnRH), and luteinizing hormone (LH) from the pituitary gland, and progesterone and estrogen from the ovaries. In order for reproduction to occur, each of these needs to be released in the correct amounts at the right times, otherwise problems with fertility may occur.
In the first phase, FSH stimulates the growth of the follicle in which the egg resides. Estrogen is released by the ovaries allowing the biggest follicle to mature. As the amount of estrogen increases, the FSH subsides and GnRH gets secreted which then stimulates a surge of LH just before ovulation.
During assisted reproduction and controlled ovarian stimulation, synthetic hormones such as cetrorelix are used to mimic the actions of these naturally occurring hormones. This process is performed with the help of a reproductive specialist and may involve daily injections of the various hormones. These may often be self-administered at home after the woman has been carefully trained in the safe and sterile administration of the injections.
The mechanism of action of cetrorelix lies in it blocking the GnRH receptors and preventing the surge of LH, therefore preventing premature release of the follicle before the egg is mature. Other hormones are administered to ensure maturation of the eggs. Once fully mature, further hormones are given to induce ovulation.
The dose of cetrorelix will differ from patient to patient depending on their fertility issues. In most cases it is given as a daily dose from day 5 until induction of ovulation with human chorionic gonadotropin. In some patients it may be given as a single dose. The prescribed dose should never be exceeded and the doctor’s instructions should be followed closely to ensure the best result.
As with any medication, cetrorelix may cause adverse side effects, most commonly local reactions. Redness, itching and swelling at the injection site, usually the lower abdomen, has been reported, as well as nausea and headache have also been reported. Should adverse effects occur, they should be discussed with the treating doctor.
