Comparisons of different combinations of analogues of PCF2 alpha and dopamine agonists for the termination of pregnancy in dogs

Groups of five pregnant bitches were treated to terminate the pregnancy wit h four combinations of drugs, starting 28 days after the estimated surge of luteinising hormone (LH), 22 to 28 days after the first mating. The treatm ents were: cabergoline administered orally for In days at a dose of 5 mu g/ kg and a single subcutaneous injection of 2.5 mu g/kg cloprostenol at the s tart of the treatment; the same dose of cabergoline plus two doses of 1 mu g/kg cloprostenol administered on days 28 and 32 after the an surge; bromoc ryptine administered orally at a dose of 30 mu g/kg three times a day for I n days plus a single dose of 2.5 mu g/kg cloprostenol; the same dose of bro mocryptine plus two doses of 1 mu g/kg cloprostenol; and a group of five pr egnant bitches was left untreated. The pregnancies were terminated in all b ut one of the treated bitches, in each case by resorption of the fetuses. T here were few side effects in the bitches treated with two doses of 1 mu g/ kg cloprostenol, and were present bur acceptable in those treated with one dose of 2.5 mu g/kg. Plasma progesterone concentrations decreased to less t han 1 ng/ml within 72 hours of the start of treatment and remained low exce pt in the bitch in which pregnancy was not terminated. In the five untreate d bitches, plasma progesterone remained high and they whelped normally. In the treated groups, the. intervals between successive displays of oestrus w ere reduced by approximately 70 days in comparison with previous cycles or with the control group, but the fertility of the dogs was not affected adve rsely.