Cetrorelix

Cetrorelix directly blocks the pituitary receptor for gonadotropin-releasing hormone. Cetrotide, its FDA-approved prescription form, is injected under the skin, usually in the abdomen, during ovarian stimulation for IVF. It prevents eggs being released before the fertility team is ready to retrieve them; it does not stimulate follicle growth itself.

Older IVF suppression protocols relied on GnRH agonists. They initially stimulated hormone release, then quieted the pituitary over roughly two weeks, creating an early flare and estrogen-withdrawal effects. Antagonists were developed to block the signal directly. Cetrotide’s 2000 FDA approval provided a shorter, faster approach, which has become a mainstream stimulation option.

Pulses of hypothalamic GnRH normally drive pituitary LH and FSH secretion. During stimulated follicle growth, rising estrogen can trigger an unwanted early LH surge. Cetrorelix competes for the GnRH receptor and rapidly, reversibly suppresses gonadotropin release without an initial flare. Suppression is dose dependent, so treatment can begin later in the cycle and last only several days.

The US product is 0.25 mg injected daily. A single 3 mg regimen was studied but is not the marketed US strength. In a multicenter randomized study, that single 3 mg dose prevented an LH surge in every participant studied and required shorter stimulation and fewer gonadotropin ampules than a long agonist protocol.

FDA approved Cetrotide in 2000 to inhibit premature LH surges in women receiving controlled ovarian stimulation. The approval concerns this specialist fertility use rather than general-purpose hormone treatment.

After gonadotropins stimulate several follicles, cetrorelix holds back ovulation until maturation and a separate trigger injection. This timing requires a monitored fertility cycle. It is contraindicated in pregnancy, severe renal impairment and known allergy to cetrorelix or other GnRH analogs.

Common reactions include injection-site redness, itching or swelling, nausea and headache. Hypersensitivity can rarely be severe. Ovarian hyperstimulation syndrome remains a risk of the overall stimulation cycle. A Cochrane review found less OHSS with antagonist protocols than with the long agonist approach, without a conclusive live-birth difference.