MPA was effective in reducing estrous production in female dogs as well as reducing testosterone levels in males. It was later removed from the market due to a high risk of cystic endometrial hyperplasia and uterine infection.[5] Another progestin-based drug, megestrol acetate, was also found to be effective in prevention of oestrus in female dogs,[5] but required administration at specific time intervals, making it unsuitable for feral animals.[3]