Cetrorelix
Cetrorelix is a GnRH antagonist used in IVF to prevent premature LH surges during controlled ovarian stimulation. It blocks pituitary GnRH receptors immediately, giving rapid, reversible suppression without the flare of agonist protocols.
01 Overview
Cetrorelix is a synthetic decapeptide GnRH antagonist. In assisted reproduction it is added during the follicular phase once follicles reach a threshold size, preventing an early LH surge that would cause premature ovulation.
Its immediate, competitive blockade means shorter, more flexible stimulation cycles than long agonist protocols, with a quick return of pituitary function after stopping.
02 Mechanism
Competitive antagonism of pituitary GnRH receptors rapidly suppresses LH (and FSH) secretion without an initial agonist flare.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Daily IVF protocol | 0.25 mg/day | SubQ | 0.25 mg SC daily from stimulation day 5-6 until trigger |
| Single-dose protocol | 3 mg | SubQ | 3 mg single SC dose covers ~4 days |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Prevents premature LH surgeBlocks early ovulation during controlled ovarian stimulation, protecting the IVF cycle. | Clinical | ||
| Rapid, reversible suppressionAllows shorter antagonist protocols with fast pituitary recovery after cessation. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site reactionsTransient redness, itching, or swelling at the subcutaneous site. | Mild | Common | Clinical | |
| Ovarian hyperstimulation riskAs part of stimulation cycles, OHSS can occur, though antagonist protocols carry lower risk than agonist ones. | Severe | Uncommon | Clinical |