AlternativeCetrotide / Orgalutran / Ryeqo (relugolix combo)
GnRH antagonists (cetrorelix, ganirelix, relugolix)
GnRH receptor antagonist
Immediate LH suppression — IVF short protocol; relugolix for fibroids/endometriosis.
SC / Oral
First-line for
- IVF short/antagonist protocol
- Uterine fibroids / endometriosis (relugolix + oestradiol + norethisterone combination)
Mechanism
Competitive antagonism at pituitary GnRH receptor → immediate ↓ LH — no flare.
"Antagonist = no flare"
- Rapid onset
- No initial worsening
- Combined tablet gives add-back
Dosing
- Cetrorelix
- 0.25 mg SC daily from ~day 5 of stim (or 3 mg single)
- Relugolix combo
- 40 mg + oestradiol 1 mg + NETA 0.5 mg PO daily
Contraindications
- AbsolutePregnancy, breastfeeding, severe hepatic disease, hormone-dependent malignancy (relugolix combo)
Side effects
- Injection-site reaction
- Headache
- With combo: BMD monitoring, VTE risk (oestradiol component)
Fetal & maternal notes
- • Contraindicated in pregnancy
Key interactions
P-gp inhibitors (relugolix)
Caution↑ exposure
Clinical pearls
- 💡 Antagonist IVF protocol shorter and lowers OHSS vs long agonist
- 💡 Ryeqo licensed up to 24 months for fibroids/endometriosis
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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