10 FAQs About the Mismate Injection Explained

1. What exactly is the mismate injection?

The mismate injection, also known as misalliance treatment, is an antiprogestagenic drug licensed in the UK for preventing unwanted pregnancy in female dogs (bitches). The medication, commonly known as Alizin and produced by Virbac, works by mimicking and competing for progesterone receptors in the uterus. By blocking these receptors, the uterus cannot maintain pregnancy, causing termination of an unwanted early pregnancy. Treatment involves two subcutaneous injections given 24 hours apart, usually administered into the scruff of the neck.

2. When can the mismate injection be administered?

For best results, the mismate injection should be given within 45 days of an accidental mating. Ideally, it is administered after the fertile heat period (oestrus) has ended but before day 45 of pregnancy.

3. How effective is the mismate injection?

When administered early—before day 22 of pregnancy—Alizin is almost 100% effective at terminating pregnancy. Effectiveness decreases slightly with administration up to day 45, with a success rate around 95%. Due to potential partial abortions or resorption of the litter, a veterinary scan approximately 4 weeks after treatment is recommended to confirm success.

4. What are the possible side effects of the mismate injection?

Alizin is generally well tolerated, but some side effects may occur. These can include temporary loss of appetite, restlessness, mild depression, vomiting, diarrhoea, and vaginal discharge associated with fetal expulsion. Occasionally, some bitches may experience an inflammatory reaction at the injection site or be at risk of uterine infection following treatment. It is usual for the treated bitch's next season to occur earlier than normal, typically 1 to 3 months sooner.

5. Does the mismate injection affect future fertility?

There is no evidence that Alizin negatively impacts the long-term fertility of bitches, as it has no residual effect. However, as abortion causes metabolic stress, many vets recommend allowing the dog to have one normal season after treatment before planning any future mating. This resting period helps the bitch's body fully recover.

6. When is the best time to have my bitch spayed after using the mismate injection?

If you do not intend to breed your dog, it is advisable to let her have her next heat naturally since it may arrive earlier than usual. Spaying after this season generally promotes better health. However, if there's a risk of another accidental mating, consult your vet about earlier neutering options.

7. How costly is the mismate injection treatment?

The cost varies depending on the veterinary practice and location. Typically, the treatment includes two vet consultations, two injections, and often an ultrasound scan to check the pregnancy's status. Later administration in pregnancy might require hospitalisation to monitor foetal expulsion. While the treatment is an investment, it may be more cost-effective compared to caring for an unplanned litter of puppies, which often presents challenges finding suitable homes.

8. Are there any health risks or contraindications?

Caution is required when using Alizin in bitches with chronic respiratory or cardiovascular conditions, particularly bacterial endocarditis. It should be avoided in those with liver or kidney dysfunction, diabetes mellitus, Addison’s disease (hypoadrenocorticism), or known hypersensitivity to aglepristone or any excipients in the product. Additionally, Alizin can reduce the effectiveness of glucocorticoid treatments, so veterinary advice is important if your dog is on such medications.

9. How soon will I know if the injection was successful?

Typically, abortion and foetal expulsion occur within seven days of treatment. However, since some bitches may partially abort or resorb the litter, the most reliable method to confirm pregnancy termination is via an ultrasound scan approximately four weeks after administration.

10. Is the mismate injection hazardous to people?

Accidental injection poses risks, especially to pregnant women or those planning pregnancy. Veterinary surgeons and those restraining the dog should take care to avoid accidental exposure when handling Alizin.

Additional Insights and Responsible Ownership

The mismate injection offers a veterinary option to manage unintended dog pregnancies responsibly. It should always be considered within a broader strategy promoting prevention through spaying or vigilant supervision to avoid accidental matings. Choosing to use the mismate injection should be done under veterinary guidance to ensure ethical, humane care for the bitch. Ultimately, well-informed and responsible pet ownership helps reduce unwanted litters, contributing positively to animal welfare in the UK.