ASPCA Statement of Support for Veterinarians Considering Megestrol Acetate as a Temporary Contraceptive for Female Cats During COVID-19
Widespread decrease in access to routine spay/neuter during the COVID-19 pandemic has raised valid concern that many cats will breed, resulting in an overwhelming number of kittens that could far outnumber available adoptive and foster homes. Making the situation even more challenging are the potentially disruptive behaviors cats may exhibit when in heat, thereby diminishing the pool of willing adoptive and foster home opportunities for cats who have not been spayed.
Therefore, the ASPCA supports veterinarians’ discretionary use of megestrol acetate as a temporary oral contraceptive in female pet cats when there is limited availability of surgical sterilization during the COVID-19 pandemic, and where the benefits of giving the medication outweigh the risks for the patient. Animal shelters with intact cats in foster homes should discuss this option with their veterinarians when it isn’t feasible to separate intact male and female cats old enough to mate and/or when the behaviors exhibited by an intact female cat may preclude that animal remaining in the adoptive or foster home.
Key takeaway: Use of Megestrol Acetate as a temporary contraceptive for female cats during the COVID-19 pandemic should be considered to address behavioral challenges and stem the tide of unchecked cat breeding.
Here’s why Megestrol Acetate is important to consider as a contraceptive option during the current crisis:
Cats can breed early and often
Female cats usually become sexually mature and come into heat between 5 and 9 months of age. In rare cases, they can get pregnant as early as 3.5 months of age (Griffin 2001). Male cats reach sexual maturity, at about 8 to 10 months of age, and they are prolific, capable of successfully breeding multiple times in a day for their entire lives (Schmidt 1986). For these reasons, and because of the difficultly in precisely estimating the age of a cat after 5-6 months of age, cats 5 months of age and older should be separated by sex unless sterilized.
Female cats usually begin to come into heat in late January or early February as the days become longer (Griffin 2001), resulting in a large number of kittens being born through the spring and summer months. Unless they become pregnant, females will come into heat every 2 weeks or so until the fall. In addition, female cats can come back into heat 2 to 8 weeks after weaning kittens, or in some cases, even while the kittens are still nursing (Griffin 2001).
Megestrol acetate provides temporary contraception for female cats
Megestrol acetate (MA) is a synthetic progestin that can be used as an orally administered short-term contraceptive for female cats (>4 months old) during the COVID-19 pandemic (ACC&D 2020). While use of the drug is not without potential risks, they may be outweighed during this time of crisis by creating greater opportunity for more cats and kittens to find adoptive and foster homes.
The lowest effective dosage commonly used in other countries for contraception and suppression of heat behaviors (0.625 mg/kg or approximately 2.5 mg/cat) appears to be relatively safe; cats already showing signs of being in heat will temporarily require higher doses. Continuous weekly oral administration of MA is necessary, as cats are expected to come into heat and could become pregnant within 1-2 weeks of discontinuation of the drug. Individual dosing and regular monitoring of treated cats for adverse effects is strongly recommended. MA does not provide contraception for male cats and is therefore not recommended for that purpose.
There has been considerable research into the efficacy and safety of MA (Romagnoli 2015); however, much of that work has looked at higher doses (>2.5 mg/cat), which may cause more frequent and severe side effects including diabetes, Cushing’s disease, and uterine and mammary problems. As with all medical treatments, the risks of using MA as a short-term contraceptive in female cats should be weighed against the need to help prevent pregnancy and to manage unwanted heat behaviors. If intact male and female cats are potentially old enough to breed and cannot be housed separately, or if foster/adoptive homes are unwilling to tolerate female heat behaviors, the use of MA may be warranted until surgical sterilization is again readily available. Veterinarians should carefully consider the benefits and risks and determine the shortest duration and lowest practical dose for the female cat if MA is used until access to routine surgical sterilization is restored. Despite potential risks, megestrol acetate is an important tool in the veterinarian’s arsenal to address an unusual challenge in a difficult time.