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The mismate injection is also known as misalliance treatment. It is an antiprogestagenic drug which is licenced for the prevention of unwanted pregnancy in bitches. It simulates the structure and competes for progesterone receptors in the uterus. Subsequently, when these receptors are blocked, the uterus cannot maintain pregnancy. The drug is called Alizin and it is produced by Virbac (available in 10ml vials containing 30mg/ml). Two injections given 24 hours apart are required. Alizin is given subcutaneously into the scruff of the neck.
It is recommended that Alizin be administered up to 45 days after the accidental mating.
Although Alizin is generally very effective, bitches that remain pregnant despite treatment should be monitored, as viability of the puppies may be compromised. Problems affecting the bitch are rare, but may include anorexia, excitation, depression, vomiting or diarrhoea. If the treatment is successful, abortion may be accompanied by fetal expulsion, vaginal discharge, reduced appetite, restlessness and mammary congestion. Some bitches may be at risk from uterine infection, and it is usual for an earlier season than normal following administration of Alizin. Occasionally, a bitch may suffer from an inflammatory reaction at the site of injection, but this is usually quick to subside.
If given before day 22 of a pregnancy Alizin is almost 100% effective. It is best given after oestrus has finished. When it is used later in pregnancy (up to day 45) it is around 95% effective.
Alizin should not adversely affect the fertility of your bitch as it has no residual action. However do be aware that abortion causes metabolic stress. Upon ethical and humane grounds you may prefer to let her have one normal season and allow her body to get back to normal completely before planning her mating for the season after. (Although of course you must be extra careful not to allow any further accidents!)
If you are not planning to breed from your bitch and want to get her spayed, it is best to allow her to have her next season normally as it may come sooner than usual (usually between 1-3 months earlier). Once she is out of season, this is a good time to consider getting her neutered. You may want to get her spayed sooner if there is a danger of her getting caught again, and your vet will be able to advise.
Price varies depending on your location. The mismate injection is not cheap, but it does include two consultations, two injections, and sometimes an ultrasound scan after 4 weeks to establish whether the treatment has been successful. If the mismate injection is given in later pregnancy your vet may also wish to hospitalise your bitch to supervise the foetal expulsion. You need to weigh up the pros and cons – it is much more expensive to bring a litter of puppies into the world, especially if they are as a result of an unplanned mating and may be very difficult to find homes for.
Extra caution must be exercise if administering Alizin to bitches with chronic obstructive-airway disease and/or cardiovascular disease, particularly bacterial endocarditis. Alizin should not be used in bitches with hepatic or renal dysfunction, diabetes mellitus, hypoadrenocorticism (Addison’s disease) or a genetic predisposition to hypoadrenocorticism. It must not be used for bitches with known hypersensitivity to aglepristone or the veterinary medicinal product excipient.
Alizin may reduce the effect of glucocorticoid treatment.
Abortion usually occurs within 7 days of administration and foetal expulsion is generally evident. However some bitches may resorb the litter, or only partially abort, so the best way to find out if the mismate injection is successful is to have her scanned 4 weeks after the treatment.
Accidental injection is a hazard to women who are pregnant or are planning to become pregnant. Care should be taken by the veterinary surgeon when handling the product and the person restraining the dog to avoid accidental injection.