Megestrol acetate

From Dog

Megestrol acetate is a steroidal progestin and progesterone derivativewith predominantly progestational and antigonadotropic effects.

It is used in dogs for:

A leading side-effect of this drug is development of cystic endometrial hyperplasia and pyometra when used for protracted periods as an estrus suppressant[1], and a greater risk of mammary tumor development, particularly the Beagle[2].

Recommended dose rate in dogs is 0.5 mg/kg once daily for eight days.


  1. Arora N et al (2006) A model for cystic endometrial hyperplasia/pyometra complex in the bitch. Theriogenology 66(6-7):1530-1536
  2. Rabe T & Runnebaum B (1986) Progestins and carbohydrate metabolism. Int J Fertil 31:31-45