Cetrorelix (cetrotide) is a medication used in in vitro fertilization to prevent eggs from being released too early. Cetrorelix can also be used to treat pain in endometriosis.

What is endometriosis?

Endometriosis is a disease where tissue resembling the endometrial tissue or the tissue that normally lines the uterus grows outside the uterus, forming lesions. These endometrial lesions are subject to the same hormonal cycle that causes the lining of the uterus to swell and shed during the menstrual cycle. The endometrial lesions, being located outside the uterus, cannot, however, exit the body like the normal endometrium, causing pain, and in more severe cases, infertility.

How Cetrorelix works

The menstrual cycle is controlled by a delicate balance of hormones that changes during the cycle. Estrogen signals to the endometrial lining in the uterus to swell in preparation for fertilization, and at the end of the cycle, to shed the endometrial layer if no fertilization has occurred. The endometrial lesions swell and shed along with the menstrual cycle.

Estrogen secretion is controlled by the gonadotropin-releasing hormone (GnRH) produced in the hypothalamus, an area of the brain considered the “master control” for hormone secretion.

Cetrorelix is a GnRH receptor antagonist. It works by binding to and blocking the receptor that GnRH normally activates. By blocking the GnRH receptor, cetrorelix prevents GnRH from signaling to the ovaries to produce estrogen. The reduction in estrogen secretion means that the endometrial lesions do not swell or spread. This reduces the pain and inflammation patients experience.

Cetrorelix in clinical trials for endometriosis

A Phase 2 clinical trial (NCT00244452) to identify effective doses of Cetrorelix to describe the dose-effect relationship and determine the duration of symptom relief has been completed. The results and the exact parameters have not yet been published.

A small study, published in the journal Reproductive Biomedical Online, described the case of 15 patients with endometriosis who received treatment with Cetrorelix once a week for eight weeks. All 15 reported no endometriosis symptoms during the time they were treated. Laparoscopy revealed that nine of the 15 patients had regressed from stage 3 to stage 2 endometriosis.

Other information

Cetrorelix can cause side effects, including bloating, nausea, headache, shortness of breath, and rapid weight gain.

Cetrorelix is marketed by EMD Serono, which is known as Merck KGaA outside the U.S. and in Canada. In Japan it is marketed by Shionogi & Co. and Nippon Kayaku.


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