Cloprostenol is a synthetic prostaglandin analogue structurally related to Prostaglandin F2α (PGF2α), for use in cattle and horses. As a potent luteolytic agent it causes functional and morphological regression of the corpus luteum (luteolysis) in cattle and horses followed by return to oestrus and normal ovulation.

Note: There is a refractory period of four to five days after ovulation when cattle and horses are insensitive to the luteolytic effect of prostaglandins. Estrumate has a good safety margin and does not impair fertility. No deleterious effects have been reported on the progeny conceived at the oestrus following treatment.

After its administration by injection, cloprostenol is metabolised to acid 9, 11, dihydroxy-15-ceto prost-5-enoic and 9, 11, 15-trihydroxyprost-5-enoic which rapidly disappear from the blood, being excreted via the urine in 5-6 hours.

Radiolabelled studies show blood levels between 0.0014 and 0.002 µg per ml at 20 minutes - 2 hours after its administration. Subsequently, blood levels fall rapidly, having an apparent half life of 1-3 hours, falling below 0.00004 µg/ml at 8 hours. No significant concentrations are found at 24 hours in the liver, muscle, heart, kidneys, uterus, ovaries, skin, brain and fat, nor in milk after 4 hours.