Pregnancy termination in bitches with a high dose of the GnRH antagonist, acyline

BLANCO P; RUBE A; TÓRTORA M; RODRÍGUEZ R; CORRADA Y; ARIAS D; GOBELLO C

Curitiba

Congreso; XVII Congresso Brasileiro de Repordução Animal; 2007

Colegio Brasileiro de Repordução Animal

Introduction GnRH antagonists competitively and immediately block GnRH receptors sites at the pituitary gland. Circulating gonadotrophins and gonadal steroids decline to very low concentrations within 2 hours of a single administration of antagonists (Vickery et al., 1989). GnRH antagonists are particularly useful when an immediate inhibitory effect on the gonadal axis is required. In female dogs, a practical reproductive situation that usually requires a rapid intervention is unwanted pregnancy termination (Gobello 2006). Safe, efficient, single dose abortive drugs have not been developed in dogs yet. The objective of this study was test the efficacy and safety of a high dose of the GnRH antagonist, acyline, on canine pregnancy termination in bitches. Additionally, progesterone (P4) serum concentrations before and after treatment were described. Materials & Methods Twelve pregnant (30 to 35 days from first mating) bitches were randomly assigned to one of the following pharmacological protocols: acyline (NIH, USA) 330g/kg sc (ACY; n = 7) or placebo (PLA; n = 5) which were administered the corresponding equal volume of bacteriostatic water sc. The animals were followed up (behavioral changes, vulvar discharge, abortion and local or systemic side effects) daily during 15 days. Blood samples for P4 (Coat-A-Count, DPC®, Los Angeles, USA) serum determinations were collected by peripheral venipuncture before and on days 2, 5, 7 and 14 after treatments. Pregnancy termination was confirmed by ultrasound monitoring on days 8 and 12 or whenever there were clinical suspicion of interruption. Progesterone serum concentrations and days to pregnancy termination of the different groups were compared by PROC GLM (SAS®). The frequency of bitches achieving pregnancy termination and/or side effects were analyzed by PROC FREQ (SAS®). Results & Discussion Significant differences were found for clinical and endocrine effects of treatments (P0.05). Progesterone serum concentrations significantly diminished in the ACY group but not in the PLA (P