Fri, 03/17/2023 - 12:52am

The ABCs of Alizin

This new drug terminates accidental breedings and treats pyometra

Is there a new drug for treating accidental breedings?


Yes, Alizin is the brand name for the drug aglepristone. It is an injection that can be given to terminate unwanted pregnancy in dogs. Alizin is also used to treat pyometra in dogs without surgery.

Progesterone is a hormone produced by the ovaries and placenta that helps maintain pregnancy. Its main effects on tissues inside the body are to encourage the growth of an elaborate network of glands in the uterus to help provide nutrition to the embryo. It also helps to develop the mother’s side of the placenta. During pregnancy, progesterone keeps the muscle layers of the uterus quiet so as not to disrupt the pregnancy.

Alizin contains aglepristone, a synthetic steroid that is a progesterone agonist. This means it competitively inhibits progesterone receptors since the chemical makeup of the molecule is similar. By binding to the progesterone receptors, aglepristone blocks the progesterone molecules from the uterine lining, thereby preventing implantation of the fertilized embryos and development of the placenta. The ability of aglepristone to bind to progesterone receptors in the uterus in dogs is three times higher than that of progesterone.

Without the influence of progesterone, the uterus contracts and the cervix dilates, expelling the contents of the uterus. Abortion occurs within a few days, thereby terminating an unwanted pregnancy. Alizin can be given up to 45 days after an accidental mating.

Pyometra is an infection of the uterus that occurs secondary to hormonal changes. After a bitch’s heat cycle, the increased levels of progesterone cause cysts to form in the uterine wall. These cysts produce large amounts of fluid, which is secreted into the uterus.

Pyometras are classified as either “open” or “closed,” depending on whether the cervix is dilated or not. This is an important factor in the severity of the disease, its prognosis and treatment options. With an open pyometra, vaginal discharge will be evident, allowing more time for diagnosis and treatment. A bitch with a closed pyometra can accumulate enough fluid in her uterus to cause it to rupture and release the infected fluid into the abdomen. Death can occur within 48 hours.

The usual treatment for pyometra is surgery to remove the enlarged, infected uterus. Most bitches with closed cervix pyometras get very sick very quickly and would not be able to respond to medical treatment. In cases where the bitch is more stable and a valuable member of a breeding program, medical treatment with Alizin has shown encouraging results.

Alizin works on pyometras in much the same way as it does to terminate a pregnancy. The aglepristone binds to the progesterone receptors in the uterus, preventing the effects of the progesterone. Consequently, the cervix opens and the uterus contracts, releasing the infected contents.


How is Alizin administered?


For termination of pregnancy, it is recommended to wait until the end of the estrus cycle to begin treatment. This is usually 10 to 14 days after the mating. An injection of Alizin is administered under strictly aseptic conditions, subcutaneously in the area of the withers, every 24 hours for two days. After the drug is injected, it is necessary to lightly massage the injection site. The abortion or fetal resorption process will start within a few days and be completed by seven days.

In cases of partial expulsion or no expulsion, the treatment can be repeated in 10 days between days 30 and 45 post-mating. If the treatment is not successful, surgery or whelping of puppies should be considered. There is no evidence that treatment with Alizin causes mutations or birth defects in puppies when treatment fails.

The efficacy when Alizin is given in the first trimester of pregnancy (up to day 21) is 99.9 percent. In the second trimester, Alizin affects the development of the placenta and the efficacy is 95 percent. After using the drug, the next estrus cycle is usually normal with normal pregnancy and whelping.

When attempting to treat a pyometra, injections of Alizin are given subcutaneously on days 1, 2 and 8 after the onset of symptoms. If necessary, an additional injection can be given on day 15. Antibiotics are also prescribed to help clear the infection. Amoxicillin, Clavamox and Baytril are the recommended antibiotics.

Electrolyte fluids are another part of the treatment to prevent dehydration and ease the strain on the kidneys. The fluids would be administered intravenously or subcutaneously, depending on the condition of the patient.

Bloodwork to monitor the white-blood-cell count, and kidney and liver function should be run. Diagnostic imaging, including radiographs and ultrasound, is used to monitor the response to treatment.

Recent studies show a high percentage of effectiveness in treating pyometra in female dogs. Some side effects were observed, including local pain and inflammation at the injection site, vomiting, excessive salivation, loss of appetite and diarrhea. All these resolved when treatment was concluded.

No bitches in the study developed pyometra on their next or subsequent heat cycles. There has been no reported effect on fertility after treatment with Alizin.


Is Alizin available in the United States?


At this time, Alizin is only available abroad and not in the United States. However, according to my sources, it can be ordered for delivery in two to four weeks. Veterinarians with a large reproductive clientele should consider having it in stock.


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