What Are the Best Flea and Tick Pills for Dogs?

Ellen Malmanger, DVM
By Ellen Malmanger, DVM on Jul. 31, 2020
close up of a black and white dog outside

Fleas and ticks aren’t just gross—they’re dangerous. Both can carry diseases that can affect your dog, and they can put people at risk as well.

Anyone who has had to tackle a flea infestation or pull ticks off of their dog knows how important it is to use a quality flea and tick prevention product. So how do you choose which is the best flea and tick pill for your dog?

All of the prescription flea and tick pills for dogs are very effective, and there are a variety of options to meet your pet’s specific needs.

Your veterinarian likely has one or two preferred products that they are the most familiar with, and they can help you find the best flea and tick pills for your dog.

Types of Flea Pills for Dogs

All oral flea prevention products have the potential to cause stomach upset, so they should be given with food. They should also be used with caution in dogs with seizure conditions, so check with your veterinarian first if you dog has a history of any neurologic problems.

Here’s a guide to the most common types of flea and tick pills for dogs.

Isoxazoline Class: Bravecto (fluralaner), NexGard (afoxolaner), Simparica (sarolaner), and Credelio (lotilaner)

The isoxazoline class of flea and tick pills for dogs is newer to the market and includes Bravecto®, NexGard®, Simparica®, Simparica Trio®, and Credelio®. It has been a game-changer because these active ingredients are very effective against both fleas and ticks. Many of these products are also used off-label to treat and control certain types of mites that cause mange.

How They Work

The active ingredients in the isoxazoline class work on the nervous system of the flea, killing it once it bites your dog.

Are There Any Safety Risks?

Because the nervous systems of mammals do not have the same receptors as those of insects, these medications have a very low risk of toxicity and are very safe.

There have been some reported cases of adverse events such as seizures, but these are very rare and seem to mainly be an issue in dogs with pre-existing seizure conditions.

Spinosad (insecticide): Trifexis and Comfortis

Trifexis® and Comfortis® are flea pills for dogs that both use the active ingredient spinosad to kill fleas. Spinosad is an insecticide based on chemical compounds found in certain bacteria.

It is important to note that these products are solely flea pills for dogs and are ineffective against ticks.

How Spinosad Works

Spinosad targets the nervous system of insects. In fact, spinosad is often used by organic farmers to control insect problems.

Are There Any Safety Risks?

Spinosad is considered to be very safe.

Sentinel (lufenuron)

Sentinel® is an insect-growth regulator, meaning that it prevents the hatching of flea eggs. Sentinel is not effective against ticks.

How Sentinel Works 

Sentinel® will not kill adult fleas, but instead prevents any future fleas from hatching, therefore controlling the flea infestation.

If your dog has an active flea infestation and is started on Sentinel for flea control, they may also need a product that kills adult fleas initially, like Capstar or Advantus.

Are There Any Safety Risks?

This product has been found to be very safe, but you should always consult your veterinarian if you are ever worried about the safety of a flea prevention product.

How Often Do You Need to Give Your Dog Flea and Tick Pills?

One thing to consider when you are weighing your options is the frequency of dosing. All of the above flea preventatives are given monthly, except for Bravecto, which is labeled for 12 weeks. It is important to note that this means it should be given every 12 weeks and not every three months, as some months have more days than others.

Some people like giving the flea and tick treatment every month along with heartworm preventative pills, because they find it easier to remember on a certain day of each month.

Other pet parents enjoy the fact that they don’t have to remember monthly dosing with Bravecto, although you will have to set a reminder every 12 weeks. The choice is yours; either way, it is recommended that you put a reminder on your calendar or in your phone so you’re never surprised with a flea infestation if you forget.

Do OTC Flea Pills Work as Well as Prescription Flea and Tick Pills?

Capstar® (nitenpyram) and Advantus® (imidacloprid) are both over-the-counter (OTC) products that kill adult fleas very quickly. They can be very useful in instances of severe flea infestations, when the adult fleas need to be killed quickly and safely.

While they work on flea infestations, they should not be used as your dog’s regular flea preventative, as they do not have lasting efficacy. Any flea larvae or eggs on your dog will still become adult fleas, and the infestation will start all over again.

If one of these products is used, it should be followed up with a prescription flea prevention product.

Can You Use Natural Flea Preventatives?

Many people are curious about natural alternatives to flea pills for dogs. A simple internet search will show a multitude of claims about bathing pets with dish soap or using garlic, brewer’s yeast, essential oils, herbs, and other natural products.

While some of these products may have a small amount of efficacy against fleas, many of these are at best not very effective, and at worst downright dangerous.

For example, garlic is toxic to dogs and can even be fatal in large enough amounts, but many natural flea remedies recommend feeding it to your pet. Many essential oils can also be toxic, and most are not made to be applied directly to the skin.

As drugs, oral flea preventatives have been extensively tested and studied, and they are approved by the Food and Drug Administration. They are proven to be safe and effective, and they are closely monitored and regulated. Natural products have no such benefit of having safety and efficacy closely scrutinized.

Are Flea Pills Better Than Topical Flea Medications and Flea Collars?

While there is no single right or wrong answer when it comes to quality flea and tick prevention, some forms may work better than others for your particular dog.

Flea Pills for Dogs: Pros and Cons

The oral tablets are great for these reasons:

  • Dogs generally enjoy them as a treat.

  • You don’t have to worry about applying them incorrectly.

  • There is no risk of the medication washing off as with topical products.

  • They can’t break off and get lost like the collars could.

Here are some drawbacks to the flea pills:

  • Your dog may refuse to eat the pill.

  • You have to monitor your dog and make sure they eat the whole pill.

Topical Flea Treatments: Pros and Cons

As for the topical flea medications, they are tried and true. They have been used for decades, and most people are very familiar with them.

Here are some more pros for topical products:

  • Many are OTC and easy to obtain.

  • They are quick to apply.

  • You don’t have to worry about a picky dog turning up their nose at the flavored oral tablets.

Here are some downsides:

  • Because they have been around for so long, veterinarians are starting to see flea resistance to a lot of these products.

  • Many people dislike having the liquid in their dog’s fur, where it can rub off on them.

  • You have to be careful about bathing, because it could reduce efficacy in some situations.

Flea and Tick Collars: Pros and Cons

Flea and tick collar efficacy can vary widely depending on the product. There are many that are not very effective, but brands like Seresto and Scalibor have been proven to work very well.

Here are some benefits to flea collars:

  • As long as they are applied correctly, they can last for eight months (Seresto) or six months (Scalibor).

  • Proven brands work well to kill fleas and ticks.

Here are some downsides:

  • If your dog is frequently bathed or loves to swim, these collars won’t be effective for as long as they would have been.

  • They could break off and get lost.

Ultimately, as long as you are diligent about protecting your dog from fleas and ticks, any of the veterinary-approved products should work great. Have a conversation with your veterinarian about what they recommend for your pet and your lifestyle.


Brianti, E., et. al. Field evaluation of two different treatment approaches and their ability to control fleas and prevent canine leishmaniosis in a highly endemic area.PLoS neglected tropical diseases. 2016.

Craig Datz, DVM, MS, DABVP, DACVN. Isoxazolines. Clinician's Brief. 2018. 

Carol Robertson-Plouch, DVM. et. al. Clinical Field Study of the Safety and Efficacy of Spinosad Chewable Tablets for Controlling Fleas on Dogs. 

U.S. Food and Drug Administration.Safe Use of Flea and Tick Products in Pets.  2021.

Featured Image: iStock.com/vyasphoto


Ellen Malmanger, DVM


Ellen Malmanger, DVM


Dr. Ellen Malmanger is originally from Arkansas, but attended Iowa State University College of Veterinary Medicine for veterinary school....

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