Ganirelix
GnRH analogues (agonists and antagonists)
GnRH analogues (agonists and antagonists)Pregnancy: contraindicated
Contraindicated in pregnancy: in animals it caused fetal loss, a predictable result of its anti-gonadotropin action; pregnancy is excluded before starting.
Injected GnRH antagonist peptide that prevents a premature LH surge during ovarian stimulation for IVF. Acts rapidly, with no initial flare.
Quick facts
- Group
- GnRH analogues (agonists and antagonists)
- Target
- Gonadotropin-releasing hormone receptor (GnRH-R) on pituitary gonadotroph cells
- Used for
- Prevention of premature LH surges
- Key effects
- Pelvic or abdominal pain · Headache · Redness
- Monitor
- Pregnancy excluded before starting · Signs of allergy
- ATC
- H01CC01
No doses: the clinician sets them by the current guideline.
Mechanism of action
Ganirelix is a synthetic decapeptide related to natural GnRH, with several amino acids replaced. It competitively blocks GnRH receptors on the pituitary, so LH (and less so FSH) falls rapidly, with no initial surge of gonadotropins. In ovarian stimulation for assisted reproduction, this stops the premature LH surge that would make the follicles ovulate before the eggs are collected. The effect wears off quickly when the drug is stopped.
- The antagonist blocks GnRH receptors in the pituitary
- LH falls rapidly, with no initial flare
- No premature LH surge: follicles wait for egg retrieval
Indications
- Prevention of premature LH surges in women undergoing controlled ovarian stimulation for assisted reproduction. Female infertility →
Adverse effects
Common
- Pelvic or abdominal pain
- Headache
- Redness, swelling or itching at the injection site
- Vaginal bleeding
Contraindications
- Known or suspected pregnancy
- Allergy to ganirelix, to GnRH or to any other GnRH analogue
- Breastfeeding
Key interactions
- Injected gonadotropins (FSH) used for stimulation
- Ganirelix suppresses the pituitary's own hormones, so the gonadotropin dose may need adjusting.
What is monitored
- Pregnancy excluded before starting
- Follicle growth by ultrasound and hormone levels, as part of the stimulation cycle
- Signs of allergy and of ovarian hyperstimulation
Administration and safety
- For subcutaneous use only, from a ready-to-use prefilled syringe.
- Usual sites are the abdomen around the navel or the upper thigh; sites are rotated.
- Started in the mid to late follicular phase of a stimulation cycle, under a fertility specialist.
- The packaging contains no natural rubber latex.
Pregnancy and breastfeeding
Contraindicated in pregnancy: in animals it caused fetal loss, a predictable result of its anti-gonadotropin action; pregnancy is excluded before starting.
Nursing care
- Confirm that pregnancy has been excluded.
- Teach self-injection technique and site rotation.
- Ask about allergies, especially to GnRH analogues; teach to report hives, swelling of the face or trouble breathing.
- Teach the signs of ovarian hyperstimulation: abdominal swelling or pain, rapid weight gain, breathlessness, less urine.
Pharmacokinetics
- Absorption
- Subcutaneous injection, rapidly and almost completely absorbed; peak in about an hour.
- Half-life
- About 13 hours after a single injection.
Test yourself
Think of the answer, then tap the question to see it.
Why are GnRH antagonists used during ovarian stimulation for IVF?
To prevent a premature LH surge, which would trigger ovulation before the eggs are collected.
How does a GnRH antagonist differ from a GnRH agonist at the start of treatment?
The antagonist lowers LH rapidly with no initial flare; an agonist first causes a surge before it suppresses.
What must be excluded before the first dose of ganirelix?
Pregnancy.
Connections
← Back to the class: GnRH analogues (agonists and antagonists)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - GANIRELIX ACETATE injection (DailyMed (U.S. National Library of Medicine), 2024); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.