GnRH antagonist

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.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

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. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Drugs

Pathways