The use of progestins in equine medicine: A review

Progesterone is in constant fluctuation throughout the lifespan of the horse. As a key regulator of the hypothalamic–pituitary–gonadal axis, progesterone is involved in numerous aspects of reproduction. Synthetic analogs of progesterone, deemed progestins, are widely available to industry to act as progestogenic within the reproductive tract, although few are bioactive in the horse. Utilised to suppress oestrous, delay ovulation, maintain pregnancy, and for behavioural modifications, progestins are a commonly administered class of pharmaceuticals in veterinary medicine. In this review, we discuss the progestins available to equine industry, in addition to assessing efficacy, pharmacokinetics, and potential side effects following administration of each.