Sylvia Masson 1, Tiphaine Medam 2, Elsa Raibon 3, Christelle Fontaine 3 and Xavier Levy 4
Deslorelin slow-released implants are registered in Europe for the reversible suppression
of fertility in male dogs. After administration, a time-limited increase in sex hormones
concentration and related behavioral problems may be observed. The aim of this work
was to assess whether cyproterone acetate, a synthetic progestogen, can prevent
this flare-up effect. Eighteen privately-owned entire male dogs were enrolled in this
double-blind, placebo-controlled, randomized clinical trial. All subjects received a 4.7mg
deslorelin implant by SC route and 1–3 capsules containing either cyproterone acetate
2 mg/kg (N = 9) or a placebo (N = 9), by oral route BID for 14 days, depending
on the dog’s weight. The dogs were followed for 28 days. An increase in the blood
testosterone concentration was observed in respectively 9/9 and 7/9 dogs of the control
and cyproterone groups (p = 0.47). However, a worsening of the sex hormone related
problems (i.e., urinary marking, mounting, aggressiveness toward other dogs and/or
escape) was only observed in the placebo group, in 56 or 66% of the dogs as measured
by respectively the veterinarian and the owners. Our study suggests that cyproterone
acetate is effective and safe to supress the deslorelin induced behavioral flare-up effect,
but not the rise in testosterone.