ATCvet Code: QG03DA04

The vaginal delivery system delivers progesterone at a controlled rate across the vaginal mucosa into the blood stream. This suppresses the release of gonadotrophin-releasing hormone and consequently luteinising hormone from the anterior pituitary inhibiting follicle maturation and so controlling the oestrous cycle. After removal of the device, circulating blood levels of progesterone fall precipitously within 6 hours, allowing follicle maturation, behavioural oestrus and ovulation.

The pharmacokinetic profile of progesterone when administered as a single device was characterised by a maximum concentration (Cmax) in plasma of approximately 4.33 ng/ml achieved at 1.19 hours post-dosing (Tmax) and an Area Under the Curve (AUC∞) of 19.47 ng/ml.hr. Peak concentrations were followed by a decline in systemic exposure with an apparent elimination half-life (t1/2) of 0.298 hours. After removal of the device, circulating blood levels of progesterone fall precipitously within 6 hours.