Friday, July 20, 2018

Edible Birth Control for Cats

It works, is low risk, *LOW COST
and can save millions of cats' lives

This blog is my opinion based on years of personal experience and dozens of hours of research. I am not a veterinarian. Megestrol Acetate is available by prescription only in the United States but can be purchased on EBAY under the name "Nonovulin". Do thorough research and give careful consideration before making your own decision about obtaining or using Megestrol Acetate.

It works -
I have used both Feralstat and Nonovulin with success for over 10 years. A colleague writes about his positive experience on Fairchild Feral Friends has used it for over a decade to stabilize colonies while T/N/R is being done. A Topix forum (please see archived posts) has caretakers from all over the country discussing their success. And it has been available without a prescription in pharmacies in Europe for more than 20 years.  

It's low risk -
The following French study took place after a consumer voiced concerns about side effects of megestrol acetate products for cat birth control. Even though the manufacturer's recommended dosage is much higher than the dose U.S. feral cat caretakers use, risk of side effects was determined to be .074 per 100K pills sold. An English translation as well as the original French study is available through the website at

My own research (see archive) showed very little research in the U.S., and all at much higher doses. A European study was more extensive and showed very low risk of adverse reaction. 

I have used Nonovulin successfully on two indoor cats for which surgery was high risk, with no negative side effects.   
It's low cost
July of 2020 I paid $16 for 30 ten mg Nonovulin pills through an EBAY vendor.  There are other sources. I have no financial or personal interest in any of these companies.My suggestion is to Google "Nonovulin" for sources or speak to your veterinarian about a prescription for Megestrol Acetate or Megace liquid. 

My colony is currently 7 cats. I use the dosage chart below and cut the 10 mg pills in half with a pill cutter and dissolve them in a little water (in a clear container so that I can see that the particles are well dissolved) before adding them once a week to two 22 oz cans of wet cat food a cost of 27 cents for the Nonovulin.   

Dosage PER COLONY  using Nonovulin 10 mg tablets

                                                Total # of Cats           Dosage (dry) per colony 

                                                       < 5 cats                       2.5 mg ONCE a week
                                                          5-7 cats                    5 mg ONCE a week
                                                          8-11 cats                  7.5 mg ONCE a week
                                                          12-15 cats                5 mg TWICE A WEEK
                                                          16-19 cats                7.5 mg TWICE A WEEK
                                                          20-23 cats                8 mg TWICE A WEEK
                                                          24-27 cats                10 mg TWICE A WEEK 
                                                          28-31 cats                11 mg TWICE A WEEK
                                                          32-35 cats                12.5 mg TWICE A WEEKc      

          2.8 ml  TWICE A WEEK                        14 mg TWICE A WEEK

This information was previously published on my site