Are Bravecto or Nexgard Safe to Use on Your Dog?

When these flea and tick preventatives first debuted, they caused an online uproar. Now, more people are giving their dogs these chewable alternatives to spot-on treatments.

Nexgard and Bravecto are chewable flea and tick preventatives for dogs. By: PixelwunderByRebecca

Your head could spin when trying to buy a flea and tick product these days.

It seems like there are a ton of new products out there, but that’s actually not true. The only truly new class of flea and tick preps on the market in the last couple of years are — drum roll, please — the isoxazolines.

To put this into brand-name English, we’re talking Nexgard (afoxolaner) and Bravecto (fluralaner), the 2 most commonly prescribed chewable tablets for flea and tick prevention. Simparica (sarolaner) hit the market in March 2016.

What to Know About the “Laners”

  • They are considered safe. More on this later.
  • They are highly effective.
  • They are chewable.
  • They are expensive.
  • They are available by prescription only.
  • They last for 3 months (Bravecto) or 1 month (Nexgard).

Until these isoxazolines were discovered, the most effective products in common use have been spot-on treatments, like Frontline and Advantix. But what are the differences, and are these new medications safe, you ask? Let’s get into it.

These preventatives aren’t so new; they’ve been around long enough to be proven safe and effective. By: akpool1021


When Bravecto came on the market in 2014, there was a lot of misinformation spread on the internet about how the product killed dogs. But there is no evidence to support these sensational claims.

The FDA concluded that although certain precautions should be taken, Bravecto and Nexgard have been in general usage now for several years and have been proven safe and effective. These products work by inhibiting the nervous system of insects. They do not affect the nervous system of mammals.

In safety studies, Bravecto was administered up to 5 times the recommended dose and given at shorter intervals (8 weeks instead of 12) with no adverse effects.

Although any drug or anti-parasitic medication can cause side effects, animal poison control, independent science journals and studies and the FDA find no evidence that these isoxazolines carry serious adverse side effects.

It is recommended not to use on dogs with a seizure disorder or on debilitated animals. The most common side effects reported have been vomiting, lethargy and diarrhea. Although the alarming online claims cannot be proven, any drug or vaccine can produce a serious reaction in a particular individual. Is the possibility of these drugs causing severe debilitation or death significant in general usage? No.

I stayed away from recommending these products when they first hit the market. Frontline and Advantix were tried-and-true alternatives, so I prescribed those. By now, however, millions of doses of Bravecto and Nexgard have been used in Europe, Canada and here in the U.S. I believe they are an appropriate alternative to the spot-ons.

Every individual must ultimately be the judge of whether or not they want to use any product highly effective against fleas and ticks on their dog or run the risk of having their dog get flea-infested or be struck with a tick-borne disease. Although fleas are an incredible pain in the neck, ticks are more ominous in that they can cause diseases such as Lyme or anaplasmosis.

Most people don’t like the idea of a topical chemical preventative on their pet. By: petraboekhoff


Independent studies conclude these drugs are highly effective in killing fleas and ticks. The only drawback is that these oral meds do not repel flea and ticks like some of the spot-ons do.

There may be a slight chance of a tick biting and spreading a disease to your pet before the tick dies. Having used Nexgard now for 2 years in an endemic tick area, I can honestly say I find more dead ticks on my dog compared to slow-moving or dying ticks that I found when using Advantix.

There are anecdotal reports and many reports from my clients that some resistance is developing to the spot-ons. Since Bravecto and Nexgard are a new class of drugs, there seems to be no or very little resistance.


The new meds cost a few more dollars a month, on average. The sticker shock with Bravecto is the whopping cost of 1 pill, around $50 a pop!

That pill covers you for 3 months, however. The company encourages a “pay as you go” policy, where they will remind and bill you for 1 pill quarterly, splitting up the cost of 4 pills over a year.

Switching From Advantix

Most of my clients switch to an oral med because they don’t like the idea of a chemical sitting on top of their furry friend’s skin. Some dogs hate the sensation of the topical and, rarely, the medication causes skin eruptions.

Most people, however, don’t want the spot-on chemical rubbing off on themselves, their children, other pets or their home surfaces. They feel giving the dog a pill means less human and environmental exposure.

Watch this review of other vet-recommended flea and tick preventatives:

By Prescription Only

These drugs will be available by prescription only for several years. You can buy them from your vet or from an internet pharmacy. If you don’t have any relationship with a vet, it could be difficult to get a script.

To sum things up, the majority of vets prescribing these products are reporting their clients are very happy. People love not putting a substance directly on their dog. Very few of my patients have vomited on the medication, but 1 dog was sick for several days. More clients had complaints about the spot-ons causing some discomfort and agitation upon application.

In my area, where people are terrified of tick-borne diseases, the isoxazolines are a welcome addition to the anti-flea and anti-tick arsenal. I completely understand that some of you will recoil at the idea of giving a systemic anti-parasitic medication to your dog. It boils down to the risk of your dog contracting a severe disease versus using a preventative that is proven safe in the vast majority of canine patients.


This pet health content was written by a veterinarian, Dr. Debora Lichtenberg, VMD. It was last reviewed May 30, 2018.

Dr. Debora Lichtenberg, VMD

View posts by Dr. Debora Lichtenberg, VMD
Dr. Debora Lichtenberg, VMD, is a small animal and exotics veterinarian who has split her time between a veterinary practice in Pelham, Massachusetts, and her studio in New York City. Dr. Lichtenberg is a graduate of the University of Pennsylvania School of Veterinary Medicine with 30 years of experience. Her special interests are soft tissue surgery and oncology.

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