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is afoxolaner safe for dogs?

3 Answer(s) Available
Answer # 1 #

It has minimal side effects, and has been shown to be safe at up to 5 times the recommended dose. In a 90-day field study, 415 dogs were administered afoxolaner and no serious adverse reactions were observed with NexGard. The most frequent adverse reaction was vomiting, with 17 dogs experiencing that reaction.

JC Froelick
Light Board Operator
Answer # 2 #

2019 Update (FINALLY): FDA issues alert for isoxazoline class of flea, tick products. Potential exists for neurologic adverse events in dogs and cats when treated with isoxazoline class products .

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.

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.

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:

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.

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:

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.

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.

Huston Lano
Answer # 3 #

Afoxolaner (NexGard®) is used to treat and prevent flea and tick infestations in dogs. It is also used as a preventive for Lyme disease. After being ingested by a dog, afoxolaner is distributed throughout the dog’s body. When fleas or ticks bite the dog, they are exposed to the drug and killed during their blood meal.

Sometimes afoxolaner is used for the treatment of sarcoptic mange, demodectic mange, cutaneous myiasis, ear mite infestations and, sand fly infestations in dogs. It is also occasionally used in cats to treat ear mites and in birds to treat Peacock louse. When afoxolaner is prescribed in these cases, it is referred to as 'extra-label' or 'off-label' use. Many drugs are commonly prescribed for off-label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully, as their directions may be significantly different from those on the manufacturer’s label.

After exposure, this medication begins to kill fleas after four hours and ticks after at least 12 hours. Keep in mind that you will likely continue to see fleas on a treated dog for some time, especially if you have a flea infestation in your home. Fleas will continue to hatch and climb onto your dog in search of a blood meal. The fleas' death prevents reproduction and new eggs being laid in the home. The more fleas that climb onto the dog and are killed, the faster the infestation will be eliminated.

Afoxolaner is given by mouth in the form of a chewable tablet. The tablet should always be given as directed by your veterinarian. It can be given with or without food or water. Be sure your dog consumes the entire dose. If your dog vomits within two hours of dosing, give another full dose. Try giving the next dose with food.

Give the missed dose as soon as you remember and start a new monthly dosing schedule. For example, if you forgot to give your dog his/her dose on June 1st and remember on June 18th, give the dose on June 18th and start a new monthly schedule. The next dose your dog will receive would be on July 18th. Do not give your dog two doses at once.

Most dogs have very few side effects from afoxolaner, provided it is given according to label recommendations and at the prescribed interval (or for off-label use, according to the directions given by your veterinarian). If you observe any vomiting, dry/flaky skin, diarrhea, lethargy, lack of appetite, or neurological signs such as incoordination, muscle tremors, or seizures, contact your veterinarian. At that time, make sure your veterinarian is aware of any other medications or natural remedies that you give your dog.

Afoxolaner should be used with caution in dogs with a history of seizures. Do not use it in pets that are allergic to it. Do not use it in dogs less than eight weeks of age or that weigh less than four pounds (1.8kg) unless instructed by your veterinarian.

Afoxolaner has not been evaluated in breeding, pregnant, or lactating dogs.

At this time, there are no known drug interactions reported with afoxolaner. Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

There is no specific monitoring required for dogs receiving afoxolaner.

Store afoxolaner-based products at room temperature (below 30°C or 86°F) in a cool, dry place, away from heat.