I saw ads for a new flea and tick insecticide on Hulu recently, and was curious about the ingredient they were using. The following post outlines the research I did on the product, and a related one I found during research.

About the product

The makers of Frontline have created a new chewable product called NexGard that can be used to repel fleas and ticks. It is similar to another product called Bravecto, also a chewable designed by another company also used to repel fleas and ticks. Both products contain a chemical derivative of isoxazolines, which are derivatives of isoxazole. All are part of the same chemical group the better-known insecticide fipronil comes from.

About the ingredients of this flea and tick preventative

The active ingredient in the flea and tick product NexGard is called afoxolaner, and the active ingredient in Bravecto is called fluralaner. They are similar chemicals, as noted above. Afoxolaner states the following efficacy:

Fleas and ticks must attach to the host and commence feeding in order to be exposed to the active substance. For fleas ( C. felis), the onset of effect (death, >95%) is within 8 hours of attachment. For ticks, the onset of effect (>90%) is within 48 hours of attachment. (Source)

If you are concerned about some tick borne diseases that may be transferred in less than 48 hours, you may want to consider other forms of repellants. This product is also not recommended for dogs who have a history of seizures, and recommends consulting a veterinarian before using with breeding, pregnant or lactating dogs. The study that demonstrated the efficacy of the product was funded by the manufacturer, something to consider in the decision making process. In other words, you may want to consider anecdotal evidence as well.

Safety of afoxolaner and fluralaner

Unfortunately, there is very little information on these drugs. Afoxolaner was recently approved in 2013, and most of the information available online points back to a study that was sponsored by Merial who patented the drug. Not only was the trial done on dogs with afoxolaner run by the manufacturer (Merial), but the trial done for Bravecto was performed by employees of Merck who sell it. Because both studies were conducted or sponsored by the companies that had vested monetary gains by them producing a positive result, I do feel that either are worthy of close study or consideration.

This, of course, is my opinion only. I do not have a lot of trust in large corporations paying for their own safety studies in order to bring a new drug to market – of which there is significant monetary gain as described here: “Under section 512(c)(2)(F)(i) of the Federal Food, Drug, and Cosmetic Act, this approval qualifies for FIVE years of marketing exclusivity beginning on the date of the approval because no active ingredient of the new animal drug has previously been approved.” (Source). Essentially, generics can be made after patents expire and this means that such companies create new products that only they can sell. Companies need to keep patenting new drugs to have this market advantage.

But what we do know is afoxolaner (NexGard) and fluralaner (Bravecto) are both part of the isoxazoline chemical class. They are commonly used against parasites, and is in the same group of chemicals as Fipronil that is widely known and understood to be a carcinogen. Chemicals in general can lead to suppressed immune systems, and suppressed immune systems can directly lead to problems like immune-mediated disease and cancer. In other words, it’s best to proceed with great caution when approaching unknown chemicals.

I do agree with the veterinarian who states in this article:

Consumers in general, and the pet-owning public in particular, need to be more mindful and questioning rather than trusting what they are told by manufacturers and our government regulatory authorities.

Because afoxolaner is part of the same class of chemicals as fipronil, and has not been independently or widely studied or on the market for long, I personally believe that great caution should be used before putting this chemical into your dog’s bloodstream.

In summary

Unfortunately I wish there was more concrete evidence that I could point you to about these products. They are new, and the only science I can find in relation to their efficacy and safety comes from, what I personally feel, is a highly conflicted source. Therefore, I can only present that the chemical is related to one that is known to be dangerous, but I can’t say with any certainty it is dangerous as well through related (unbiased) study or anecdotal evidence as the product is so new.

I do invite you to weigh in your own concerns, or share any anecdotal evidence you have experienced or found. I don’t doubt that the product could be quite effective, but I always do caution people to carefully consider the long-term risks of any chemical – especially new ones that have yet to prove themselves – that is used regularly and directly enters the bloodstream and can suppress the immune system or cause issues that we just don’t know about yet.

UPDATE: There are two very active groups on Facebook about these two drugs. There are regular postings added about dogs who are experiencing similar and severe side effects not long after taking these drugs, suggesting there may be a link between the two. Do remember that this is anecdotal evidence, but it can be useful to help arrive at a decision provided the limited studies and limited time the drug has had on the market.
Bravecto group
Nexgard group

Note: I am not a veterinarian. Please consult a trusted professional before administering any of these or similar drugs to your dog. If you are not sure, ideally seek a vet without vested interest in a related purchase.

About Author

Jen deHaan is graphic designer, small business owner, and dog person living in Bay Area, California. Jen enjoys learning about dog training and behavior, and has taken several courses and seminars since 2010. She also contributes articles to leading websites, such as Victoria Stilwell's Positively . It all started with a great dog called Mikey (aka "dude"), loved and lost but remembered forever. Jen also runs a freelance business focusing on graphic, web, and UI design at FoundPixel, and a small business creating hand crafted dog products at Stylish Canine.