Norgestomet is a synthetic derivative of progesterone with improved oral activity due to its 17α-acetate side chain. In veterinary medicine norgestomet is used for the synchronisation of oestrus in cattle. It is administered as a subcutaneous ear implant (containing 3 mg norgestomet; to be removed after 9 to 10 days), in combination with a single intramuscular injection containing 3 mg norgestomet and 5 mg oestradiol valerate. The injection is to be given immediately after application of the implant. Norgestomet is not used in human medicine. It is a steroidal progestin of the 19-norprogesterone group.

Estradiol benzoate is the synthetic benzoate ester of estradiol, a steroid sex hormone vital to the maintenance of fertility and secondary sexual characteristics in females. As the primary, most potent estrogen hormone produced by the ovaries, estradiol binds to and activates specific nuclear receptors. This agent exhibits mild anabolic and metabolic properties, and increases blood coagulability. Although estradiol benzoate is not approved by the FDA for use in humans in the United States, it is approved for veterinary use as a subdermal implant both alone (CELERIN®) and in combination with the anabolic steroid trenbolone acetate (SYNOVEX® Plus).