Are These Chewable Flea And Tick Preventives Safe For Dogs?

05 Feb.,2024


Like every dog owner, you want to avoid fleas on your dog and in your home. And you don’t want your dog picking up ticks and risking tick-borne disease.

Wouldn’t it be convenient to just give your dog a tasty chew every month or 3 months to protect her from fleas and ticks? Well, in the last few years, some new flea and tick preventives for dogs let you do just that.

Great! Problem solved… or is it?

No, it’s not! If you got excited about the idea of a longer term chewable flea and tick medicine … stop right there!

These drugs have a dark side. Keep reading to learn about their sometimes deadly side effects.

What Are Chewable Flea And Tick Preventives?

There are three drugs in the category of chewable flea and tick preventives: Nexgard, Bravecto and Simparica.

Nexgard (active ingredient afoxolaner) and Bravecto (fluralaner) were approved in the US in late 2013 and early 2014. Simparica (sarolaner) came out in March 2016.

The dosing schedules are once a month for Nexgard and Simparica and once every three months for Bravecto.

How Oral Flea And Tick Preventives Work

These flea treatments are oral medications. The drugs come in a soft chew that your dog can eat like a treat. After your dog takes the chew, the drugs circulate in the blood, and when a flea or tick bites your dog, it’s exposed to the chemical. This will kill fleas and ticks.

All three drugs are pesticides that work by attacking the nervous system of the fleas and ticks, causing death. The excerpts below from the manufacturers’ Prescribing Information explain the mode of action of these drugs (we added some bold to highlight the important parts) …

Nexgard (afoxolaner)

“Afoxolaner is a member of the isoxazoline family, shown to bind at a binding site to inhibit insect and acarine ligand-gated chloride channels, in particular those gated by the neurotransmitter gamma-aminobutyric acid (GABA), thereby blocking pre- and post-synaptic transfer of chloride ions across cell membranes. Prolonged afoxolaner-induced hyperexcitation results in uncontrolled activity of the central nervous system and death of insects and acarines.

Bravecto (fluralaner)

“Fluralaner is for systemic use and belongs to the class of isoxazoline-substituted benzamide derivatives. Fluralaner is an inhibitor of the arthropod nervous system. The mode of action of fluralaner is the antagonism of the ligand-gated chloride channels (gamma-aminobutyric acid (GABA)-receptor and glutamate-receptor).”

Simparica (sarolaner)

“The active substance of SIMPARICA, sarolaner, is an acaricide and insecticide belonging to the isoxazoline group. Sarolaner inhibits the function of the neurotransmitter gamma aminobutyric acid (GABA) receptor and glutamate receptor, and works at the neuromuscular junction in insects. This results in uncontrolled neuromuscular activity leading to death in insects or acarines.

So, these chewable drugs work by destroying the insects’ nervous systems. If it’s deadly for fleas and ticks, how might it affect a dog? Remember … these drugs stay in your dog’s bloodstream for extended periods of time.

That means … once your dog takes one of these drugs, if she has any side effects, you can’t remove the drug from her body.

What Adverse Drug Event Reports Say

Dog owners often ask, “What is the safest flea and tick prevention for dogs?” Well, it’s not these chewable drugs.

Every drug has side effects and so we wanted to review the Adverse Drug Event Reports submitted to the FDA. But the FDA has made it near-impossible to find these ADE reports on their database. Luckily, thanks to veterinarian Dr Elizabeth Carney, we were able to find some information.

Back in November 2014, when Nexgard and Bravecto were first introduced, Dr Carney wrote about the new chewable drugs on her blog. And then she started receiving comments from people whose dogs were already experiencing side effects after taking these preventives. She wanted to find out more. So she filed a Freedom of Information Act (FOIA) request to obtain the reports and received a number of ADEs for Nexgard and Bravecto. Dr Carney has generously made these reports available on her website.

ADE Reports For Nexgard And Bravecto

There are specific ADE reports for Nexgard and Bravecto for the period January through March 2016. The results are very similar for both drugs. Dr Carney didn’t get any reports for Simparica as it was too new at the time.

Vomiting, lethargy and diarrhea are the most common side effects reported. Seizures are quite high on both lists, with 22 each for both Nexgard and Bravecto for the first quarter of 2016. Nine deaths are reported for each drug for the same period.  For Nexgard, five of the nine deaths were by euthanasia.

Is Nexgard Safe For Dogs?

Is Bravecto Safe For Dogs?

What Dog Owners Say About Chewable Flea and Tick Preventives
Facebook is another source of information about the side effects of these chewable drugs. These group pages contain many tragic stories from dog owners who believe their dogs have been harmed by these pest preventives.

Some of these groups have tens of thousands of members … so the risks are real!

Some of the posts are fascinating as well as alarming. One poster reports finding dead ticks on her dog as long as 12 months after his last dose of Bravecto … suggesting that’s how long it stays in your dog’s bloodstream!

So again, a reminder that if your dog experiences an adverse effect … you can’t just stop using it and expect your dog to return to normal!

Is Simparica Safe For Dogs?

Simparica hasn’t been out as long … so there’s less information. But the drug works just like Bravecto and Nexgard … it destroys flea and tick nervous systems. So it’s very likely that the adverse effects of this chewable drug are similar to the other two drugs.

The manufacturer’s website provides this warning …

Simparica may cause neurologic signs such as tremors, unsteadiness and/or seizures in dogs with or without a history of neurologic disorders. 

If you want to see the kind of effect Simparica can have on your dog, click on this video link. Be warned, though … the video is horrifying to watch. It shows a dog having a really long seizure after taking Simparica. This poor dog died a few months later because of his seizures.

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Vets Agree These Drugs Aren’t Safe
Dr Carney, who obtained these reports from the FDA, told us that she has personally decided not to use these chewable drugs for her own dog, nor will she prescribe them to her clients.Many other holistic vets are speaking out about the dangers of these long-lasting preventive products too. Check out this Facebook post by Dr Josie Beug:

The FDA has also issued Face Sheet about “potential adverse events associatd with Isoxaline Flea and Tick Product.” The FDA specifically warns that “Isoxazoline products have been associated with neurologic adverse reactions, including muscle tremors, ataxia, and seizures in some dogs and cats.

Please don’t sacrifice your dog’s health for these “convenient” chewable options. It’s a really dangerous trade-off.

RELATED: Find out how we rank flea and tick prevention – from riskiest to safest …

You can avoid harmful pest preventives for your dog. There are lots of natural, safe options. You might have to work a little harder … but your dog is worth the effort!

If you have any questions on what is sarolaner. We will give the professional answers to your questions.