Effect of an Injectable Cabergoline Formulation on Serum Prolactin (PRL) and Milk Secretion in Early Postpartum Beagle Bitches

Introduction - Cabergoline (Galastop®) is currently used as an oral formulation to reduce or eliminate mammary secretion in pseudopregnant bitches using treatment protocols which include daily administration for periods of 4-6 days (come da registrazione). An injectable formulation of cabergoline (Galastop® Iniettabile) was recently evaluated for marketing purposes. This paper describes the results of a clinical & pharmacodynamic study conducted with the injectable formulation of cabergoline administered to lactating Beagle bitches and its effects on serum prolactin concentrations and mammary milk secretion.

Materials and methods - The study was conducted on 5 adult Beagle bitches of 1-5 years of age and 8-13 kg body weight. Each bitch was inseminated using semen of an adult, healthy male Beagle dog and followed up during pregnancy. On day 3, 4 and 5 postpartum (PP) a 5.0 cc blood sample was collected AM and PM; on day 6 a 0.1 ml/kg placebo (vehicle only) was administered, and on day 9 a similar amount of injectable cabergoline formulation (containing 15 mcg/ml) was administered. All treatments were made SC between the shoulder blades, in the morning. Blood samplings were continued AM and PM until day 12 PP and then only PM until day 17 PP (table n° 1). During the 14-day study period the experimental bitches were checked twice daily to monitor weight, health status, milk production and occurrence of side effects due to treatment. Puppies’ body weight was checked twice daily and, if necessary, their nutrition was integrated with a commercially available canine milk replacement (Sherley’s Lactol) 4 times daily until the third week of age. Milk production was assessed subjectively on each bitch by looking at mammary status and trying to express milk from each teat, using the following score:

4) milk flows out in large quantity just by touching the teat;
3) milk can be expressed in large quantity when squeezing the teat;
2) milk can be expressed by squeezing the teat;
1) small amounts of milk can be expressed by squeezing the teat;
0) no milk can be expressed by squeezing the teat.

Serum PRL was assayed using an ELISA technique (Milenia Biotec Grnbh Bad Nauheim, Germany) specific for canine PRL, which has a range of calibration of 0.4-80 ng/ml and a minimum detectable concentration of 0.4 ng/ml. Data were analyzed with a one-way ANOVA using each bitch as her own control and considering the study period as the variation factor; the Tukey’s test was used to check for statistical significance of different values observed with ANOVA, and the Pearson’s correlation test was used to check for presence of correlation among all parameters studied. [...]