GnRH antagonist Pregnancy: Contraindicated during pregnancy and breast-feeding. There are no adequate data from use in pregnant women; in animals, exposure at the time of implantation resulted in litter resorption, and the relevance of these data for humans is unknown. It is not known whether ganirelix is excreted in breast milk.

Ganirelix

Brand names: Orgalutran, Fyremadel

A gonadotrophin-releasing hormone (GnRH) antagonist used during controlled ovarian stimulation to prevent premature luteinising hormone surges in assisted reproduction.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 0.25 mg

Route: Subcutaneous injection, preferably in the upper leg (vary the injection site to prevent lipoatrophy)

Frequency: Once daily, starting on day 5 or day 6 of FSH administration (or on day 5 or day 6 following administration of corifollitropin alfa), and continued daily up to the day that sufficient follicles of adequate size are present

Indication: prevention of premature LH surges in women undergoing controlled ovarian hyperstimulation (COH). Should only be prescribed by a specialist experienced in the treatment of infertility. COH with FSH or corifollitropin alfa may start at day 2 or 3 of menses. The starting day of ganirelix depends on the ovarian response — the number and size of growing follicles and/or the amount of circulating oestradiol; the start may be delayed in the absence of follicular growth, although clinical experience is based on starting on day 5 or day 6 of stimulation. Ganirelix and FSH should be administered at approximately the same time, but these medicinal products should NOT be mixed and different injection sites are to be used. FSH dose adjustments should be based on the number and size of growing follicles rather than on circulating oestradiol. TIMING OF THE LAST INJECTION (SPC §4.2): because of the half-life of ganirelix, the time between two ganirelix injections, and the time between the last ganirelix injection and the hCG injection, should not exceed 30 hours, otherwise a premature LH surge may occur. Therefore, when injecting in the morning, continue ganirelix throughout the gonadotropin treatment period including the day of triggering ovulation; when injecting in the afternoon, give the last ganirelix injection in the afternoon prior to the day of triggering ovulation. Final maturation of follicles is induced by administering hCG. Ganirelix has been shown to be safe and effective in women undergoing multiple treatment cycles; the need for luteal phase support in ganirelix cycles has not been studied. Safety and efficacy have not been established in women weighing less than 50 kg or more than 90 kg. There is no relevant use in the paediatric population. The patient or her partner may perform the injections if adequately instructed and with access to expert advice. For cross-reference, the US label in the same bundle gives the same dose expressed as 250 micrograms subcutaneously once daily, started after initiating FSH therapy on Day 2 or 3 of the cycle and continued daily until the day of hCG administration.

Dose adjustments

Renal

Contraindicated in moderate or severe renal impairment — there is no experience of use in subjects with renal impairment, as they were excluded from clinical studies (SPC §4.2/§4.3). The same applies to moderate or severe hepatic impairment. No graded dose adjustment is stated.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Hypersensitivity to gonadotropin-releasing hormone (GnRH) or any other GnRH analogue
Moderate or severe impairment of renal or hepatic function
Pregnancy or breast-feeding

Side effects

Local skin reaction at the injection site, predominantly redness with or without swelling (very common; generally resolves within 4 hours of administration)
Headache (uncommon)
Nausea (uncommon)
Malaise (uncommon)
Hypersensitivity reactions including rash, facial swelling, dyspnoea, anaphylaxis (including anaphylactic shock), angioedema and urticaria — reported as early as with the first dose (very rare); worsening of pre-existing eczema

Interactions

No interaction studies have been performed; the possibility of interactions with commonly used medicinal products, including histamine liberating medicinal products, cannot be excluded

Clinical monograph

How it works

It competitively blocks pituitary GnRH receptors, rapidly suppressing LH (and FSH) release and thereby preventing a premature LH surge and early ovulation.

Prescribing in practice

Hypersensitivity reactions can occur and treatment should only be used under specialist fertility supervision as part of a stimulation protocol.
It is given by subcutaneous injection and is contraindicated in pregnancy and breastfeeding.
Used as part of an assisted reproduction cycle, so timing relative to gonadotrophins and the ovulation trigger must follow the protocol.

Monitoring

Monitor the stimulation cycle with ultrasound and hormone levels to time the antagonist and ovulation trigger appropriately.

Counselling the patient

Follow injection technique and timing instructions carefully as part of your treatment cycle.
Local injection-site reactions may occur.
Report any signs of a severe allergic reaction immediately.

Evidence & guidelines

GnRH antagonist protocols are an established alternative to agonist protocols in NICE-supported assisted reproduction.

Reference: NICE CG156; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Drugs

Pathways