The Recent FDA Approval for Ayradia: What You Need to Know

On October 11, 2023, the Food and Drug Administration (FDA) approved the drug Ayradia for the treatment of Giardia duodenalis in dogs. Ayradia is the first FDA-approved animal drug for treating this infection in dogs.

What is Giardia Duodenalis?

Often referred to simply as Giardia, it is a microscopic protozoan parasite that affects the gastrointestinal tracts in canines. This single-celled organism resides in the small intestine and is responsible for a condition known as Giardiasis,

Symptoms of giardiasis generally including:

• loose stools
• swelling of joints and eyes
• over time, can cause weight loss and prevention of the body absorbing essential nutrients

Symptoms normally begin one to two weeks after becoming infected; it can last anywhere between two and six weeks although potentially lasting longer in those with weakened immune systems.

The life cycle of Giardia involves two distinct stages: cysts and trophozoites.

Giardia Cysts

The cysts are shed in the feces of infected dogs and can survive in that environment, allowing for easy transmission. Dogs typically contract Giardiasis by ingesting contaminated water or foods, although direct contact with infected feces can also contribute to transmission.

Giardia Trophozoites

When a dog ingests the cysts, they transform into the trophozoite form inside the small intestine, which attaches to the internal lining of the intestine. This causes damage, interferes with nutrient absorption, and results in gastrointestinal problems, including symptoms such as lethargy, weight loss, vomiting, and diarrhea.

Giardiasis is a common parasitic infection in dogs, particularly in environments with compromised levels of hygiene. Diagnosis can be challenging, as symptoms may resemble those of other gastrointestinal issues. While not all infected dogs show signs of illness, younger dogs or those with weakened immune systems are more likely to experience symptoms. Giardia can be spread to other animals and is a parasite with zoonotic potential, meaning it can spread to humans as well. While you’re unlikely to become infected with Giardia from your dog, it's still best to practice good hygiene to minimize your risk of exposure.

Diagnosis and Treatment of Giardia

Diagnosing Giardiasis in dogs involves a complete history, physical examination, and specific tests to check for evidence of infection. Veterinarians typically use fecal tests to detect the presence of Giardiasis in the dog's stool.

Typical treatment involves antiparasitic medications, in addition to thorough cleaning and management of the surrounding environment to prevent reinfection. The treatment goal is to eliminate the infection, but it can be challenging to do so.

Follow-up evaluation after the completion of treatment is advisable to assess how effective the initial intervention is.

What is Ayradia?

Ayradia (metronidazole oral suspension) is the first FDA-approved animal drug for treating Giardia infections. Metronidazole is not a new medication, up until this point it’s been an approved human drug, used off-label to treat dogs with a Giardia infection.

This new version of the medication has some changes compared to its predecessor.

• It’s been tested on dogs now having statistical proof of its efficacy and safety.
• Comes in a chicken flavor making the liquid more palatable to dogs.

Ayradia has both antibacterial and antiprotozoal properties. The sponsor, Virbac Animal Health, based in Fort Worth, Texas, conducted two key studies on Ayradia:

Laboratory Study

Male and female beagles were given either Ayradia or sterile water orally twice per day for five consecutive days. The study counted the Giardia trophozoites in each dog's small intestine four days after the final treatment. Ayradia was found to be over 99% effective at reducing Giardia trophozoites in the treated dogs compared to the control group.

Field Study

A similar field study was conducted using shelter and privately owned dogs with naturally occurring infections. Dogs received either Ayradia or only the inactive ingredients in Ayradia (i.e. no metronidazole) for five consecutive days.

Fecal samples were obtained before and after treatment, showing that dogs treated with Ayradia had significantly fewer Giardia cysts than those in the control group, confirming Ayradia was more than 99% effective at reducing Giardia cysts.

Safety Studies

Safety studies were also conducted to address two factors: higher than label dose and duration and labeled dose and duration. Dogs that had the higher than label dose experienced a higher incidence of ear erythema (redness of the skin and ear) and diarrhea, but these issues resolved without treatment.

Considerations When Using Ayradia

Additional neurologic effects have been associated with the use of Ayradia oral suspension at high doses in dogs. Therefore, it should be used with caution in dogs that have hepatic dysfunction, which refers to impaired liver function. Hepatic dysfunction can occur due to various causes such as toxicity, infection, and liver disease.

When the liver loses more than 75% of its function, it is deemed to have hepatic failure, leading to a range of symptoms impacting other organ systems. Common signs of hepatic dysfunction in dogs include diarrhea, vomiting, anorexia, lethargy, polyuria (increased urination), polydipsia (increased thirst), ascites (abnormal fluid accumulation in the abdomen), jaundice, diarrhea, neurological abnormalities consistent with hepatic encephalopathy.

Virbac recommends avoiding contact with a treated dog's saliva for five minutes after administration.

Dosage and Precautions

Ayradia is administered orally at 25 mg per kg of body weight, using the supplied syringe, twice daily for five consecutive days. Ayradia is only available by prescription from a licensed veterinarian, as professional expertise is essential to properly diagnose Giardia duodenalis infection in dogs and monitor the safe use of the product, including treating any adverse reactions.

As Ayradia is a skin sensitizer, it can potentially cause allergic reactions in humans. While it is best practice to keep dog food away from children, pet owners should be careful to keep dog food that has been mixed with Ayradia away from children. In other words, while treating your pup with Ayradia, be sure to pick up uneaten food and wash their bowls more frequently.

Ayradia has been shown to effectively reduce post-treatment counts of the Giardia parasite in dogs. However, it's essential to consider the potential risks and benefits of any medication. While Ayradia can be an effective treatment for Giardia duodenalis infection in dogs, its use should be carefully evaluated in consideration of the individual dog's health and any potential risks.

With the approval of this drug, it is an exciting step forward in the treatment of Giardia duodenalis which can be a prominent presence in dogs in certain environments. It's important to note that even healthy animals may harbor a number of subclinical infections, such as Giardia duodenalis, which can result in the infection being underdiagnosed. Because asymptomatic dogs can still spread the infection, it’s important to practice good environmental hygiene measures and prevent dogs from drinking surface water or eating feces.