Ganirelix
Ganirelix is a GnRH antagonist used in IVF to prevent premature LH surges during ovarian stimulation. It gives immediate, dose-dependent pituitary suppression and is a mainstay of the shorter antagonist stimulation protocol.
01 Overview
Ganirelix is a synthetic decapeptide GnRH antagonist closely related to cetrorelix. Administered as a daily 0.25 mg subcutaneous injection during the mid-to-late follicular phase, it competitively blocks pituitary GnRH receptors and suppresses endogenous LH.
Because it has no agonist flare, it allows a shorter, patient-friendlier stimulation cycle than long agonist down-regulation and rapidly reversible suppression once stopped.
02 Mechanism
Competitive GnRH-receptor antagonism produces immediate, dose-dependent suppression of pituitary LH and FSH release without an initial flare.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| IVF antagonist protocol | 0.25 mg/day | SubQ | 0.25 mg SC once daily from stimulation day 5-6 until trigger |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Suppresses premature LH surgePrevents early ovulation during controlled ovarian stimulation. | Clinical | ||
| Enables short antagonist protocolShorter overall stimulation with fewer injections than long agonist regimens. | Clinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Injection-site reactionsLocal redness and swelling, usually resolving within hours. | Mild | Common | Clinical | |
| OHSS contributionOvarian hyperstimulation can occur within the stimulation cycle; antagonist protocols reduce but do not eliminate risk. | Severe | Uncommon | Clinical |