While NexGard COMBO is a popular choice for feline parasite prevention, a recent study highlights a potential risk for a subset of cats. This risk is linked to a genetic condition known as the MDR1 mutation, which can cause severe reactions to certain medications, including eprinomectin, an active ingredient in NexGard COMBO. Understanding this risk is crucial for cat owners to ensure the safety and well-being of their pets.
The Connection Between NexGard COMBO, Eprinomectin, and the MDR1 Mutation
NexGard COMBO and similar products like Centragard contain eprinomectin, an effective ingredient against various parasites in cats. For the vast majority of cats, eprinomectin is safe and well-tolerated when used as directed. However, a study from Washington State University’s Program for Individualized Medicine has identified a significant concern for cats carrying the MDR1 genetic mutation.
The MDR1 mutation impairs a cat’s ability to process certain drugs. Normally, a protective mechanism prevents specific substances, like eprinomectin, from entering the brain. In cats with the MDR1 mutation, this mechanism is deficient, allowing eprinomectin to cross the blood-brain barrier and potentially cause serious neurological toxicity. Dr. Katrina Mealey, the lead researcher and a veterinarian at WSU, emphasizes that while eprinomectin itself isn’t inherently problematic, the genetic predisposition in some cats creates a significant risk.
This research stemmed from an increase in reported adverse reactions in cats after eprinomectin-based products became available in the US. The WSU team analyzed medical records of 33 cats who experienced severe illness or death following treatment with eprinomectin products. After ruling out other potential causes, they found a strong correlation with the MDR1 mutation. In fourteen cases where no other cause was identified, eight cats were homozygous for the MDR1 mutation (carrying two copies of the mutated gene). Alarmingly, three of these eight cats died. These findings, published in the Journal of Veterinary Pharmacology and Therapeutics, underscore the serious risks for MDR1-mutated cats treated with eprinomectin.
Recognizing Symptoms and Understanding the Risks
Adverse reactions to eprinomectin in sensitive cats can manifest in a range of alarming symptoms. These can include loss of coordination, excessive drooling (salivation), tremors, partial paralysis, dilated pupils, coma, seizures, and tragically, even death. Notably, some cats in the study also experienced temporary tongue dysfunction, struggling to retract or fully use their tongues for days or weeks after NexGard COMBO application.
It’s important to note that symptoms may not appear immediately. Due to the topical application and delayed absorption of products like NexGard COMBO, clinical signs can be delayed for several hours. Therefore, close observation of your cat for up to 12 hours after application is crucial if you suspect they might be sensitive to eprinomectin.
Genetic Testing: A Proactive Step for Cat Owners
Dr. Mealey strongly advocates for genetic testing to identify cats with the MDR1 mutation. She, in fact, discovered the MDR1 mutation and developed the first diagnostic test for it. Genetic testing is the only definitive way to determine if your cat carries this mutation. Dr. Mealey recommends testing all cats, ideally during kittenhood. Knowing your cat’s MDR1 status allows your veterinarian to make informed decisions about medication choices, ensuring that only safe drugs and appropriate dosages are administered. In over half of the cases studied by WSU, genetic testing could have preemptively identified at-risk cats and prevented severe adverse events.
Conclusion: Informed Decisions for Your Cat’s Health
The research from Washington State University provides critical information for cat owners considering NexGard COMBO or similar parasite preventatives. While these products are generally safe, the risk to cats with the MDR1 mutation is significant and potentially life-threatening. Understanding this genetic predisposition and considering genetic testing are vital steps in responsible pet ownership. By being informed and proactive, you can work with your veterinarian to choose the safest and most effective parasite prevention strategy for your feline companion, ensuring their health and well-being. Increased awareness and potential labeling changes by the FDA are hoped to further protect cats with the MDR1 mutation.
