Friday, June 20, 2014

Edible Birth Control for Cats
It works, is low risk, and with mass distribution could save millions of cats' lives. 

Historically the only option for people like me who were feeding stray cats and wanted to do the responsible thing and keep them from reproducing was a process called Trap/Neuter/Return or T/N/R.  

In 2009 I happened upon the "Feralstat" site. After a phone consultation with their veterinarian, a non-profit in Connecticut could prescribe a powdered birth control - megestrol acetate (MA) and lactose powder - which when added weekly to wet cat food would prevent pregnancy in female cats after the second dosing. (MA is a synthetic hormone prescribed for people under names like "Megace" and pets under trade names like  "Ovaban".) 

I did hours of research (see the three posts for megestrol acetate) with sources including PubMed, part of the National Institute of Health site. The risk of side effects from MA seemed to average less than one half of one percent even at much higher dosages than Feralstat ( approx. 1 mg MA per cat once a week.) Since then I've come across a 2003 French report -" COMMISSION NATIONALE DE PHARMACOVIGILANCE VETERINAIRE RAPPORT D’EXPERTISE DE PHARMACOVIGILANCE relatif à l’AVIS CNPV – 02 du 9/12/2003" - which concluded that the risk of adverse reactions was .074 per 100K pills sold. (MA has been available in France for over a decade, through pharmacies, without a prescription.)

I also researched Tait's Every Animal Matters, the Connecticut non-profit which distributed Feralstat, and Dr, John Caltabiano who developed it. I found nothing to call in to question their credibility or ethics. 

So I ordered Feralstat and from 2010 - 2011 a colleague and I dosed 15 cats. There were no births or pregnancies. And I have used Nonovulin (megestrol acetate and powdered milk tablets )from Veniviet for the last five years (2014-2018) with no pregnancies or side effects.  

My experience is not unique. A  Topix forum (link does not always work - Google "Topix ACC&D Statement Feralstat" then click "LAST" for most recent posts, or see the archived pages here dated May 2014) includes caretakers successfully using MA. The Fairchild Foundation in Berk's County Pennsylvania has used it for years. And again, it has been available through pharmacies in Europe for over a decade.  

Feralstat ceased being distributed after the untimely death of the Dr. John Caltabiano who had filed the FDA paperwork. Megestrol acetate is available through veterinarian's with a  prescription. Nonovulin, manufactured in Bulgaria, is available again through EBAY as of March 2017. It can also be ordered through  or Both require that you email them with the product you want and pay through a wire transfer service. I have no financial or personal interest in any of these companies. .


Total # of Cats           ML Dosage(liquid)  per colony                  Dosage (dry) per colony 
< 5 cats                                .5 ml ONCE a week                             2.5 mg ONCE a week
5-7 cats                             1.0 ml ONCE a week                              5 mg ONCE a week
 8-11 cats                          1.5 ml ONCE a week                             7.5 mg ONCE a week
12-15 cats                         1.0 ml  TWICE A WEEK                        5 mg TWICE A WEEK
16-19 cats                         1.5 ml  TWICE A WEEK                        7.5 mg TWICE A WEEK
20-23 cats                         1.6 ml  TWICE A WEEK                        8 mg TWICE A WEEK
24-27 cats                         2.0 ml  TWICE A WEEK                        10 mg TWICE A WEEK 
28-31 cats                         2.2 ml  TWICE A WEEK                        11 mg TWICE A WEEK
32-35 cats                         2.5 ml  TWICE A WEEK                        12.5 mg TWICE A WEEK
36-39 cats                         2.8 ml  TWICE A WEEK                        14 mg TWICE A WEEK
40 + cats                            3.0 ml  TWICE A WEEK                        15 mg TWICE A WEEK

This information was previously published on my site