This past week the U.S Food and Drug Administration (FDA) approved a new label claim on Nexgard, a monthly oral flea and tick preventive for dogs. The new label approval states that Nexgard prevents infection with Borrelia burgdorferi, the bacteria that causes Lyme disease.
Research presented to the FDA to substantiate the new label claim measured transmission of the bacteria after exposure to infected ticks. The data demonstrated that transmission was prevented as a direct result of killing the ticks quickly enough to prevent injection of the organism into the dogs.
A similar study using another monthly oral tick preventive, Simparica, was published in 2016. Although no label claim against Lyme was added after that study, it did show 100% prevention of bacterial transmission in dogs exposed to infected ticks. Of course, nothing is 100% effective in the real world, but these studies are demonstrating that veterinarians now have exciting new tools to combat tick-borne illnesses in dogs.
Q: Are oral flea and tick preventives safe?
A: In general, these products are all very safe for most dogs. However, any oral medication or topical pesticide can have side effects in sensitive individuals. That’s why it’s important to consult your veterinarian before deciding on a specific product for your specific pet.
One safety study administered Nexgard at five times the label dose to puppies starting at eight or nine weeks of age. Three doses were administered at four-week intervals, then the doses were administered every fourteen days for three more doses. These young puppies were receiving five times the label dose twice as often as usually instructed!
With most medications or pesticides, that high of a dose would kill them, or at least cause serious illness. (In other words, don’t try putting five flea collars on your dog at the same time!) Yet, in this study, “there were no clinically relevant effects related to treatment on physical examination, body weight, food consumption, clinical pathology (hematology, clinical chemistries, or coagulation tests), gross pathology, histopathology or organ weights.” That’s an extremely impressive safety margin!
Other similar products are also quite safe, although it’s important to note that there are differences in safety profiles between brands. Any of the products in this class should be used with caution in dogs with a history of seizures. As mentioned before, it’s very important to speak with your pet’s veterinarian before choosing any product for your pet.
Another good reason to discuss any parasite control with your veterinarian is that some products can have confusing twists in their instructions. For example, Bravecto is labeled for administration every three months for fleas and certain ticks. However, to be effective against other ticks in our area it needs to be given every eight weeks. Similarly, the Seresto “8-month” flea and tick collar should be replaced every five months if your dog swims regularly or gets frequent baths.