Medicines & protocols
Antagonists act within hours, so they are started partway through stimulation and stopped at the trigger. They are the basis of the most common Canadian IVF protocol and allow an agonist trigger to be used when OHSS risk is high.
Also known as: antagonist injection, cetrorelix, ganirelix
Related Canada guides
Sources
- Canadian Fertility and Andrology Society (CFAS)
Last reviewed: September 9, 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.