April 10, 2020 by By Mike Greenberg, DVM, Director of Outreach Programs, Maddie's Fund®

Audience: Executive Leadership, Public, Veterinary Team

Why now? Why me?

In 2014, I had the honor of helping start a high-quality-high-volume spay-neuter clinic in Nashville and serve as medical director. I don't know how many thousands of dogs and cats I spayed and neutered during my tenure there, but it was enough that my hands still remember how when I'm fortunate enough to go back for relief shifts. The last relief shift I worked was March 17th, 2020. My beloved clinic had to temporarily close on March 18th due to COVID-19. Like many similar clinics, the dedicated staff there has been asking, "What can we do?"

For those of us involved in spay-neuter services, halting our efforts has raised concerns about losing ground with progress we have made, particularly in cats. One option that some have considered is the use of a temporary contraceptive, megestrol acetate in female cats, to prevent pregnancies while our spay-neuter efforts are on hold.

Non-surgical methods of contraception and sterilization have long been a passion of mine. I hope for the day when we can say to our younger colleagues, "Yeah, it was crazy. We used to have to cut animals open and remove organs just to control fertility!" While megestrol acetate is certainly not the panacea, it is a tool in the toolbox. Of course, questions surround the use of this drug: we answer some of the most common ones below.


  • Megestrol acetate (MA) is a drug that can be used to prevent cats from going into heat and getting pregnant. It can be used to "halt" estrus in cats.
  • Low-dose MA can be used to "buy time" while waiting for spay surgery
  • Low dose maximizes efficacy and minimizes side effects: 0.625 mg/kg once per week (about 2.5 mg per average adult cat)
  • Microdosing (0.1 to 0.2 mg/kg) on a per-cat basis has been used in colony situations
  • You need a prescription from a veterinarian to use it
  • This use is "off label;" off-label use of drugs is very common in veterinary medicine
  • Cost: Very affordable. Varies by compounder. Liquid formulations least expensive

Frequently Asked Questions

Bio photo of Dr. Mike Greenberg smiling in front of a light background

Michael (Mike) Greenberg, DVM, Director of Outreach Programs, Maddies' Fund®

Prior to joining the team at Maddie's Fund, Dr. Mike served as program director for Target Zero, helping communities across the US achieve 90% or greater live release rates from their animal shelter systems through implementation of best practice strategies. Following veterinary school, Mike worked in rural private practice. It was there that he began volunteering with shelters and working with shelter staff and leaders to address community issues to increase lifesaving. Having caught "the bug," Mike took the plunge into the sheltering world, and completed his training in shelter medicine with the Maddie's® Shelter Medicine Program at Cornell's College of Veterinary Medicine in 2011. Since that time, he has worked clinically and as a consultant for multiple public and private animal shelters throughout the United States. He is based in Nashville, TN where he helped to start Pet Community Center, a shelter intake prevention organization.