Ask questions when dog presents for mismate management

Q. Could you provide a practical review on mismate management ofdogs?

AAt last year's American Veterinary Medical Association Annual Convention,Dr. Bruce E. Eilts, DVM, MS, diplomate of ACT from the Louisiana State UniversitySchool of Veterinary Medicine presented an excellent review on mismate managementin dogs and possible drugs used. The practical content of the lecture isprovided below.

If a dog is presented for mismate management (abortion shot), severalquestions should be asked before any drug therapy is instituted. The answersto these questions may be:

* Was the dog really in heat?

Do a standard vaginal cytology smear to see if the dog is really in estrus.If not, then the chance of pregnancy is minimal.

* How long was the dog gone?

In that time could mating have actually happened? Since natural matingtakes up to 30 minutes, a dog that is gone for only five minutes has verylittle chance of being mated.

* Did mating occur?

Check for sperm cells in the vaginal cytology. The presence of spermcells definitely indicates that the dog has been mated, however, their absencedoes not mean that she has not been bred.

* Are puppies wanted now or in the future?

Is this really a breeding female? Why are puppies wanted? If puppiesare not wanted or wanted for a groundless reason (to make the female a betterdog), ovariohysterectomy may be the preferred alternative. If possible,have the owner pay for a non-estrual surgery now and then return when thedog is not in estrus.

* What are the chances the dog is actually pregnant?

In a study performed to look at pregnancy rates of dogs presented formismate, 62 percent of dogs presented after mating were not pregnant. Ifovariohysterectomy is not an option according to the owner, then waitingto determine if the dog is pregnant is probably the best alternative. Pregnancyexamination can be performed by ultrasonography as early as 16 to 18 daysafter the first day of diestrus. If the owner wants immediate action, thensome drug alternatives are available.

Mismate arsenal

Estradiol cypionate (ECP) is probably the only standard mismate drugavailable in the United States. ECP increases the motility and facilitatesrapid transport of the fertilized eggs in the oviduct and uterus and thusprevents implantation. There are very few academicians who will considerusing ECP today because of the risks of adverse side effects.

When used properly and for the correct owner, however, it can be relativelysafe and efficacious. The preferred dose is 44 mcg/kg (0.02 mg/lb) - notexceeding a total dose of 2 mg and given once intramuscularly during estrus.It is important that the dog is not allowed to mate again.

It is not effective if used during proestrus or diestrus; therefore,it is essential that the vaginal cytology be examined before ECP administration.

ECP can induce pyometra if given during diestrus, thus be sure the doghas not entered diestrus when ECP is administered. The dog may show sideeffects such as continued estrous signs, because of the estrogen influence.Cystic endometrial hyperplasia can also result after ECP administration.Bone marrow suppression can be dose-related or non-dose related. To avoiddose-related marrow suppression, do not give a second injection. Non-doserelated bone marrow suppression could be totally avoided only by never givingECP injections. Pyometra is not seen when the ECP was given during estrus;however, if given during diestrus there is an excellent chance of inducingpyometra.

If puppies are wanted in the future and the owner is aware that thereis a risk associated with ECP administration and the owner is willing totake the risk, then ECP offers an inexpensive, efficacious, relatively safemismate management. However, if the dog is a valuable breeding bitch ora surrogate child, then other alternatives may be more attractive to theowner and veterinarian.

Prostaglandin use

Prostaglandins are not really a true mismate drug for dogs but can beused before pregnancy is recognized. The prostaglandin product Lutalyse(Pharmacia Animal Health) is most commonly used in the dog. Prostaglandinswere originally not considered to be luteolytic until the last one-thirdof diestrus (40 days or more); however, it is now known that multiple injectionsof prostaglandins are luteolytic after only the fourth or fifth day of diestrus.

A dose of 250 mcg/kg subcutaneously daily for four days starting at dayfive to eight of diestrus is about 80 percent effective at inducing abortion.If the treatment fails, the pregnancy will be normal. Serum progesteroneconcentrations must be less than 2.0 ng/ml for 24-48 hours to result inabortion. Side effects of prostaglandins include transient vomiting, diarrhea,hyperpnea, hypersalivation and hypothermia. These side effects usually subsidewithin 30 minutes of onset. There is also the possibility of circulatoryshock, so it is important that an intravenous catheter is in place and fluidsare available to manage the shock. The shock too is transient. Generally,side effects will diminish as the prostaglandin administration continues.Prostaglandin-induced luteolysis may cause some dogs to return to estruswithin two to eight weeks.

Dexamethasone

If the dog is pregnant, then dexamethasone can be used. A dose of 5 mgintramuscularly twice daily for 10 days at gestation of 30 days abortedfour bitches one to three days after the end of treatment. In 15 bitches,dexamethasone was given at a dose of 0.1-0.2 mg/kg orally twice daily forthree doses, then 0.2 mg/kg daily on days two to five, then a decreasingdose from 0.16 to 0.02 mg/kg daily for the last five doses (total dosingdone within 7.5 days). All dogs aborted or resorbed their pregnancy twoto 26 days from beginning of dexamethasone treatment.

Eilts recommends just using the high dose orally twice daily until signsof pregnancy have disappeared. Just as in using prostaglandins, if medicalmanagement is blindly followed without doing pregnancy examinations, thentreatment failures will occur. Normal litters have been obtained after thistreatment. Side effects include a transient polydipsia/polyuria that subsidedwhen the treatments are stopped.

Prolactin

Because prolactin is luteotropic and is needed to maintain normal pregnancy,prolactin antagonists will cause an abortion. These prolactin antagonistsalso shorten the interestrus interval and prevent mammary development.

Bromocriptine mesylate (Parlodel, Novartis Pharmaceuticals) at a doseof 30-100 mcg/kg orally twice daily for five to six days at 35 to 40 daysof gestation causes abortion in three to five days. Bromocriptine may causedogs to vomit and have inappetence, and it has not been widely accepted.The long-term effects of bromocriptine on reproduction also have not beenstudied.

Cabergoline (Dostinex Tablets, Pharmacia) at a dose of 5 mcg/kg orallyfor five days after mid-late gestation causes abortion in three to fivedays after treatment with minimal side effects.

A combination of cabergoline (1.0 ug/kg, two subcutaneous injections,four days apart) and an injectable synthetic prostaglandin cloprostenolsodium (Estrumate, Schering-Plough Animal Health - 5.0 mcg/kg orally dailyfor seven days) starting day 25 after the LH peak proved 100 percent effectiveand had no side effects. The treatment does cause a shortened interestrusinterval.