What is a GnRH antagonist used for?

A GnRH antagonist blocks the action of gonadotrophin-releasing hormone quickly. This reduces the signal that could otherwise trigger a rise in luteinising hormone and an unplanned release of an egg. During ovarian stimulation, that control gives the fertility team time to monitor follicle development and plan the next step.

It does not replace the medicines used to help follicles grow. Instead, it is added at a point chosen by the fertility team, often after stimulation has begun. The product may be given as a small injection under the skin, with timing tailored to the cycle.

Follow the injection instructions and timing carefully, and keep monitoring appointments. Tell the clinic about allergies, other medicines and any previous reaction to fertility drugs. Mild redness or discomfort at the injection site can happen. Report symptoms that concern you rather than taking an extra dose or changing the schedule yourself.

Contact the fertility team urgently for severe pelvic pain, rapid abdominal swelling, repeated vomiting, breathing difficulty, fainting or reduced urination during stimulation. Seek emergency help for swelling of the lips or throat, wheezing or collapse after an injection.

Ask when to start the antagonist, what to do if an injection is late, and how it fits with your stimulation and trigger medicines. Ask which scan or blood-test findings guide the next dose and which warning symptoms need same-day advice.