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Megestrol Acetate (MA) can be used to safely contracept cats for a short period of time.

Hypothesis: Using MA to suppress estrus in cats for a short period of time will mean fewer births of kittens, and the cats in the colony will remain healthy. 

Depopulation Strategy: Short term use of MA in an area without access to a veterinarian, until the veterinary MASH unit can be deployed to surgical sterilize the population, is the most effective use of resources and an appropriate humane animal management strategy.

Currently: Animal Balance is offering microdoses of MA to the feeders of cats on Isabela Island, Galapagos Islands.

Cost: MA costs $20 to produce 100 tablets at a compounder. 1.1 mg is put into the cats good once a week.

Timing: We do not recommend doing this for longer than 6 months. It is a stop gap measure until the vet tram can be on site.

If you are interested in contracepting your cats until a vet team arrives, please email 


Click here for the instructional PowerPoint by Mike Greenberg DVM

Other sources of information:

Alliance for the contraception in cats and dogs -

Alley Cat Allies –

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