In vitro activity: Estradiol cypionate is a synthetic ester of the natural estrogen, estradiol. Compared to other commonly used estradiol esters, via the intramuscular route, estradiol cypionate is found to have the longest duration of action with a duration of ~11 days, while estradiol benzoate and estradiol valerate are found to last for 4-5 days and 7-8 days, respectively. Estradiol cypionate has several indications for use in bovine medicine. These include treatment of anestrus in the absence of follicular cysts, persistent corpus luteum, pyometra, and retained placenta. Potentially, ECP may benefit high-risk postpartum cows by stimulating uterine contractions either directly or through maintenance of oxytocin receptor sites in the uterus, bringing more WBCs to the site of infection by increasing blood flow to the uterus, enhancing uterine immune function by increasing phagocytosis of bacteria or movement of IgA and IgG into the uterine lumen, or promoting uterine drainage by delaying closure of the cervix.

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