Low-dose megestrol acetate revisited: a viable adjunct to surgical sterilization in free roaming cats?

Approximately 2-3 million cats are euthanased in animal shelters across the United States annually. Preventing pregnancy in cats is a key step to reducing this number. While surgery is generally a safe and effective tool for curbing reproduction in cats, it is not a practical method to achieve the reduction in numbers required for an appreciable impact on the cat population as a whole. Low-dose megestrol acetate (MA) is a synthetic progestin that has been used for the management of reproduction in free roaming cat populations; however, there has been no regulatory oversight regarding the use of this product for this purpose. Additionally, there is a paucity of data regarding the safety and efficacy of the product for the management of reproduction in free roaming cats. The purpose of this review is: (1) to outline the need for a non-surgical contraceptive in cats; (2) to discuss the uses of MA in domestic cats; (3) to consider potential adverse effects of the drug, and (4) to discuss regulatory challenges associated with the use of MA in free roaming cat populations. In order to answer the questions posed in this review, more data will need to be collected in laboratory and field studies.