Updated September 25, 2026. Fact-checked against veterinary sources; review by a licensed veterinarian is in progress. See our editorial policy.
Quick answer: In the United States, there’s no medication routinely recommended to stop heat cycles in pet dogs and cats. Older hormonal drugs, such as megestrol acetate, can cause serious side effects, including uterine infection (pyometra), diabetes, and mammary tumors, and are rarely used. Hormone implants are available in some other countries but carry their own trade-offs. Spaying is the reliable, permanent way to prevent heats, and management techniques help in the meantime.
Why hormonal drugs are rarely used
- Risk of pyometra, a life-threatening uterine infection
- Diabetes and weight gain
- Mammary tumors
- Behavior changes
Safer options
- Spaying: prevents heats, pregnancy, pyometra, and, if done early, greatly lowers mammary cancer risk
- Management during heat: keep females away from intact males, use dog diapers, and keep cats indoors
See dog in heat and cat in heat.
What to avoid
- Human birth control or hormone products
- Supplements claiming to stop heat
- Online hormone products without a vet
Talk to your vet if
- You’re planning breeding and need to delay a heat
- Your pet has health issues that affect spay timing
- Heats are unusually frequent or prolonged
Sources
- Merck Veterinary Manual: Contraception in small animals
- Merck Veterinary Manual: Pyometra in small animals
- American Veterinary Medical Association (AVMA): Spaying and neutering
This article is for general education and is not a substitute for care from your own veterinarian. Learn about The Pet Vet and our editorial policy.