Vol. 5 No. 1 (2019)
Case Report

Use of Cyproterone Acetate in 2 cases of unresponsive offensive social aggressions

Sylvia Masson
Clinique de la Tivolliere 37 rue des martyrs 38340 Voreppe
Gérard Muller
Clinique Vétérinaire de Lille Saint-Maurice 112, rue du faubourg de Roubaix 59800 LILLE

Published 2019-07-23


  • Case report,
  • cyproterone acetate,
  • aggresive behaviour


Canine aggressions remain one of the main reasons for euthanasia or abandonment.  

The neurophysiology of aggression is still incompletely known, but several agents have been reported to play a role in its mechanism: androgens, cortisol, and serotonin. This explains why selective serotonin reuptake inhibitors are commonly used as primary pharmacological treatment. Most dogs can improve with environment and behaviour modifications associated with such medication.  However, in severe cases, they may not completely manage aggressive behaviour or underlying anxiety, and multiple medications may be required. That's why cyproterone acetate, a combined androgen antagonist and antigonadotropin, has been proposed. This particular progestin has a wide range of mechanisms of action, including interactions with serotonin and γ-aminobutyric acid, which explains why cyproterone acetate isn’t acting like a simple testosterone reducer, but can be used in a similar way as antipsychotics.

We present 2 cases of dogs exhibiting offensive social aggression (primary dysocialization and dysthymia) despite their primary treatment. In each case, the addition of cyproterone acetate led to a decrease in number and intensity of social aggressions; and the aggressions resumed after its removal. In addition, selected cases included male and female, neutered or not, which suggests that cyproterone acetate can be useful in the treatment of offensive social aggressions.

The main side effect reported is a mild increase in appetite, which could have been more important without the primary medication (e.g. fluoxetine). Further studies including more cases are needed to investigate these preliminary findings.