Pregnancy termination in the bitch and queen

Abstract

Mismate or pregnancy termination is one of the most common "reproductive" requests from dog and cat owners. Ovariohysterectomy is the best alternative for those clients who do not really have a valid reason for keeping a reproductively intact animal. If the animal is a potential breeder, drugs are available that can prevent or terminate pregnancy. The use of these drugs must be based on the safety, efficacy, convenience, compliance in treatment, and cost of the drug. Drugs that can be given during estrus to prevent pregnancy include estrogens and tamoxifen. However, because most dogs presented for mismate are not truly pregnant, a pregnancy examination should be performed before any drug is given to terminate pregnancy. If a dog is known to be pregnant, multiple doses of natural or synthetic prostaglandins can be used throughout pregnancy, whereas multiple doses of prolactin inhibitors (cabergoline, bromocriptine, metergoline) or dexamethasone can be used in the second half of pregnancy. Combined protocols of prostaglandin and prolactin inhibitors are also effective at terminating pregnancy. Progesterone blockers such as mifepristone and aglepristone are effective, but very expensive. Other drugs, such as the isoquinolones and progesterone synthesis inhibitor epostane are available outside of the United States and appear to be very effective at terminating pregnancy. No drug, however, meets all the following criteria of a perfect mismate drug: possible to give at any stage of estrus or pregnancy, 100% effective, causes no vaginal discharge, has no side effects, does not impair future fertility, is readily available, and is inexpensive.