10 Essential FAQs About the Mismate Injection for Dogs

1. What is the mismate injection?

The mismate injection, sometimes called misalliance treatment, is an antiprogestin drug approved in the United States veterinary field to prevent unwanted pregnancies in female dogs (bitches). Known commercially as Alizin and manufactured by Virbac, this medication works by blocking progesterone receptors in the uterus. By inhibiting these receptors, the uterus loses its ability to support pregnancy, leading to termination of an unintended early pregnancy. The treatment typically consists of two subcutaneous shots administered 24 hours apart, usually given into the loose skin at the back of the neck.

2. When should the mismate injection be given?

For optimal outcomes, the mismate injection should be administered within 45 days following an accidental breeding. Ideally, the injection is given after the female dog's fertile heat cycle (estrus) concludes but before the 45th day of pregnancy.

3. How effective is the mismate injection in terminating pregnancy?

When the injection is given early, especially before day 22 of gestation, Alizin offers nearly 100% success in ending pregnancy. Effectiveness slightly decreases to about 95% when administered up to day 45. Due to possible partial miscarriage or absorption of the embryos, veterinarians usually recommend an ultrasound scan around four weeks post-treatment to confirm the pregnancy has ended successfully.

4. What side effects might occur with the mismate injection?

Generally well tolerated, Alizin can still cause some temporary side effects. These include a brief loss of appetite, restlessness, mild lethargy or depression, vomiting, diarrhea, and vaginal discharge related to fetal expulsion. Occasionally, injection site inflammation or a risk of uterine infection may develop. It's common for the treated female dog’s next heat cycle to start earlier than usual, often between one to three months sooner.

5. Does Alizin impact a dog’s future ability to reproduce?

Research shows no long-term effects of Alizin on future fertility, as it leaves no residual impact. Because abortion induces metabolic stress, many veterinarians recommend waiting for one normal reproductive cycle before planning a future mating to allow the dog’s body to recover fully.

6. When is the ideal time to spay after using the mismate injection?

If you do not plan to breed your dog, it’s generally best to allow her next heat cycle to occur naturally, which may arrive earlier than normal. Spaying after this heat is considered healthier. However, if you are concerned about the potential for another accidental breeding, discuss with your veterinarian about possibly scheduling an earlier spay.

7. What is the cost of administering the mismate injection in the US?

Costs vary based on veterinary clinics and regional location. Typically, treatment includes two veterinary visits, two injections, and often an ultrasound to assess embryonic status. Administering the drug later in pregnancy might require hospital monitoring to manage fetal expulsion. While the initial expense might be significant, it is usually more economical than caring for an unexpected litter, which can involve finding appropriate homes and additional care expenses.

8. Are there any health warnings or contraindications?

Alizin should be used cautiously in female dogs with chronic respiratory or cardiovascular diseases, especially bacterial endocarditis. It is contraindicated in dogs with liver or kidney impairment, diabetes, Addison’s disease (hypoadrenocorticism), or known allergies to aglepristone or formulation components. Moreover, this drug may reduce the effectiveness of glucocorticoids, so consult your veterinarian if your dog is receiving steroid treatment.

9. How soon will I know if the treatment worked?

Typically, fetal expulsion or abortion happens within seven days of receiving the injections. Some dogs might partially abort or reabsorb the pregnancy, so the most reliable confirmation is an ultrasound scan about four weeks after treatment to verify the pregnancy has been successfully terminated.

10. Is handling the mismate injection hazardous to humans?

Accidental injection can be dangerous, especially for pregnant women or those trying to conceive. Veterinarians and handlers should exercise caution to avoid accidental exposure when administering or handling the medication.

Additional Notes on Responsible Pet Care

The mismate injection provides a practical veterinary approach to managing unplanned dog pregnancies responsibly. It should be part of a comprehensive plan that prioritizes prevention, such as spaying and closely supervising female dogs to prevent accidental matings. Using this treatment requires veterinary oversight to guarantee humane and ethical care for the dog. Thoughtful, informed pet ownership helps lower the number of unwanted litters, supporting overall animal welfare throughout the US.