Vet Guide on Flea Pills for Dogs

There is a large variety of flea-preventative products for dogs available today. Not every product is right for every pet, however, and it is important for pet owners to take a closer look at how each category of preventatives works. For many pet owners, flea pills for dogs are the right fit, and these products have also been extensively researched.

I'm often asked about the best dog flea preventatives in my clinic, and when flea pills for dogs are brought up, the first thing I mention is that pet owners need to be very careful about the type of flea pills they choose. While there are many products that are completely safe for your Fido, there are others that can have severe side effects. You need to ensure that you only purchase products that have been evaluated by the Food & Drug Administration (FDA) and/or the Environmental Protection Agency (EPA).

It's true that flea pills for dogs are the most convenient way to protect your pet against these parasites because it takes the least time and effort, especially when compared to flea drops or flea collars, which can sometimes be a nuisance for the owner and the dog. These pills can be easily concealed in your dog's food or treats, so it's likely that he will swallow them without any issues, too.

In this guide, I will answer the most common questions about the safety and efficacy of flea pills for dogs and how to shop for the right type. However, if you have any specific questions about the best flea-preventative for your dog, you should call your veterinarian. Your vet knows your dog's health history and can recommend the best preventative for your pooch based on the region that you live in, which is very important.

ALSO READ: Veterinarian’s Guide on Flea Collars for Dogs

Flea Pills for Dogs
Veterinarian's Tips and Buying Guide

Flea Pills for Dogs

Know Your Enemy—The Flea

In order to understand how flea pills for dogs work, it is necessary to have a grasp on the basic life cycle of the flea. The type of flea that most commonly plagues our canine companions is actually the cat flea—Ctenocephalides felis.

Fleas undergo 4 basic life stages—the egg, the larva, the pupae (like a cocoon), and the adult. The adult flea is the one that causes itching and skin infections and can even carry other parasites like tapeworms. Killing just the adult flea will not effectively prevent further infestation. The most successful products to treat fleas will kill the flea in multiple spots during the life cycle, thus preventing re-infestation.

Flea Pills for DogsWhile the scope of this article is to look at flea pills, it is important to note that full flea control sometimes takes multiple approaches—including treatment of the environment. Regular vacuuming, laundering all bedding, blankets, pillows, and throws, and speaking to a reputable pest control provider can help control stubborn infestations.

Be aware that not all flea pills are safe for cats. If you are interested in flea pills for cats, talk to your veterinarian. The products included in this article only contain information for use in dogs.

Benefits of Flea Pills for Dogs

  • Kill adult fleas much faster than topicals or flea collars
  • No oily or sticky residue
  • No restrictions on bathing or swimming
  • Less concern about residue exposure to children or other pets
  • More likely to provide consistent and effective flea prevention
  • Longer duration of effective prevention
  • Many flea pills also contain heartworm prevention medication

Disadvantages of Flea Pills for Dogs

  • Most only kill the adult flea and not any intermediate life stages
  • It may cause side effects, including vomiting
  • Increased cost compared to topicals or flea collars
  • May need a veterinary prescription
  • Some products require twice-monthly or daily dosing to be effective
  • Some pets may be allergic to flavorings or additives

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Flea Pills for Dogs

Different Flea Pill Brands To Try

The 24-hour Flea Fix

Capstar (Novartis)

  • Important facts: Capstar Fast-Acting Oral Flea Treatment for Dogs Flea pill – non-chewable
    • Kills adult fleas within 30 minutes
    • Protection Lasts 24 hours
    • Very safe for most dogs and cats

The first type of flea pill available for dogs contains nitenpyram, also known as Capstar (Novartis). These flea pills for dogs only kill adults. It contains a type of drug called a neonicotinoid, which selectively inhibits insect-specific nicotinic acetylcholine receptors – essentially paralyzing the adult flea.

This is a very safe drug for dogs and cats. Given by mouth, it is rapidly absorbed into the body and is effective within 15-30 minutes. Fleas typically start to die 30 minutes after you give it. The drug does not last long in the dog’s body, roughly 24 hours.

The most common side effect reported is temporary itchiness of the dog. This is thought to be due to the fact that the fleas are dying. Dosing every day is possible and likely safe but not recommended. It is used in pets as small as 2 pounds (< 1 kg) body weight. In some countries, Capstar is available over-the-counter, while in others, it is by veterinary prescription only.

Capstar is a good option for very young puppies and kittens who are not old enough for other flea preventatives. Fleas can be life-threatening to young animals, and Capstar works quickly to prevent life-threatening flea bite anemia.

Once-a-Month Flea Preventatives

1. Sentinel (Novartis)

  • Important facts:
    Sentinel Flea Pills for Dogs
    • Flavored flea pill
    • Protection Lasts 30 days
    • Does not kill adult fleas
    • Very safe for most dogs

This flea pill contains a drug called lufenuron. Lufenuron does not kill the adult flea, but it does kill the immature life stages of the flea. Controlling fleas using this product involves environmental control. There can be a lag time of up to 6 weeks before its preventative measures take effect.

Some dogs have been on Sentinel for many years and it works well in their situations. It is not typically recommended for dogs in high-flea-burden areas or outdoor pets. Rare side effects include seizures. Not recommended for dogs prone to seizures. Sentinel is available by prescription only, as it also contains medication to prevent heartworms.

2. Comfortis and Trifexis

  • Important facts:Comfortis Flea Pills for Dogs
    • Chewable, Flavored Flea Pill
    • Once a month
    • Kills fleas within 30 minutes
    • Protection lasts 30 daysTrifexis Flea Pills for Dogs
    • Safe for most dogs

Both Comfortis and Trifexis contain the same compound for flea prevention: spinosad. The difference between Comfortis vs. Trifexis is that Comfortis treats and prevents fleas ONLY. Trifexis prevents heartworms, fleas, and intestinal parasites (roundworms, hookworms, and whipworms).

Spinosad begins to kill adult fleas within 30 minutes of giving the tablet. In a heavily flea-infested area, environmental control is necessary to help break the cycle within the first month. Spinosad works well because it kills adult fleas before they have a chance to lay eggs throughout the month.

Both Comfortis and Trifexis are chewable, beef-flavored tablets given by mouth once a month. Spinosad works by activating nicotinic acetylcholine receptors in the flea’s nervous system. Occasional vomiting is noted, especially if the dose is not given with a full meal.

If vomiting occurs within an hour of administration, another full dose may be given safely. Do not use Comfortis or Trifexis if your pet is being treated with ivermectin for demodecosis. If you don’t live in an area with heartworm risk, Comfortis may be a good option for your dog.

3. NexGard (Boehringer Ingleheim)

  • Important facts:
    NexGard Flea Pills for Dogs
    • Flavored tablet
    • Once a month
    • Kills adult fleas
    • Kills ticks
    • Safe for most dogs

NexGard contains the active ingredient afoxolaner. Afoxolaner works in a similar way to other drugs, it kills fleas by over-stimulating the flea’s nervous system. The makers of NexGard boast that it kills 100% of fleas on the dog within 24 hours. The most common side effects are vomiting, itching, diarrhea, and lethargy. 

Beyond Once-a-Month Preventatives

1. Simparica (Zoetis)

  • Important facts:
    Simparica flea pills for dogs
    • Flavored tablet
    • Kills adult fleas
    • Kills ticks
    • Safe for most dogs
    • Give once monthly – flea-killing action lasts up to 35 days

At the time of publishing, the newest monthly flea pill on the market is Simparica. It contains sarolaner, a drug similar to afoxolaner—killing fleas by interfering with the nervous system at the level of the GABA-gated chloride channels.

It is “novel” in that it works at a completely different site in the flea’s nervous system than older drugs like ivermectin and fipronil. These flea pills for dogs kill fleas within the first 8 hours of administration and last up to 35 days.

A recent study in a heavily flea infested home setting showed that when Simparica was given monthly for 3 months, there was a 95.6% reduction in adult fleas in the home within the first 14 days. Complete control was reached (near 100%) at 90 days.

Simparica is currently only licensed in the US for use in dogs over 6 months of age. Side effects may include vomiting, diarrhea, and, rarely, seizures. Do not use it on pets that have seizures.

2. Bravecto (Merck)

  • Important facts:Bravecto Flea Pills for Dogs
    • Flavored tablet
    • Give once every 12 weeks
    • Kills adult fleas
    • Kills ticks
    • Safe for most dogs

One of the newest flea preventatives on the market, Bravecto, contains a compound called fluralaner. Similar to afoxolaner, it kills fleas by over-stimulating their nervous system. It is given by mouth once every 12 weeks, and these flea pills for dogs begin to kill fleas within hours of administration.

While less frequent dosing can be convenient, many owners need a reminder in place to remember to give the tablet every 12 weeks. Possible side effects include itching, vomiting, diarrhea, and seizures. Do not use in dogs with a history of seizures. It is currently only licensed in the US for dogs over 6 months of age.

In Conclusion…

Regulations regarding the prescription availability of any of the above-mentioned and many other flea pills for dogs can vary by country. Some dog flea preventatives and treatment products are licensed for use in certain age groups of canines.

Once again, it's crucial that you talk to your veterinarian – he or she can help you find the dog flea pill that is right for your specific pet, for the region where your pooch spends the most time, and for your budget. And if you have an infestation at home, you can always use things like electric flea traps, powders, and other tools to prevent further flea problems.

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Flea Pills for Dogs - The Vet’s Buying Guide for Pet Owners

Dana is a qualified veterinarian with background in animal care and training sciences and an avid writer on the topics of dog health. Her range of expertise is wide but her primary focus in on animal nutrition and specifically dog foods.