Nexgard vs Frontline | The Ultimate Tick & Flea Treatment

Let’s face it, one of the worst parts about dog ownership is dealing with the critters they drag in, especially when it comes to fleas and ticks.

Not only are these parasites just plain gross, getting an infestation in your home can be a costly fix. In addition, flea and tick-borne illnesses are no joke for your dog or the rest of your family.

Two of the most popular products on the market for flea and tick control are NexGard and Frontline. This article is a complete and comprehensive look at both of these products, along with an in-depth look at their ingredients and how they work.

If you want to decide whether Frontline or Nexgard is better, this is a great resource to make sure you are informed with the facts before you have a conversation with your vet.

First, we will look at each of these products in turn, then we will compare them to help you decide which is best. We will also provide you with a handy table so you can compare them at a glance.


Nexgard vs Frontline: A Review

Frontline Plus®
Frontline Gold®
Nexgard®
Nexgard Spectra®

Product Image

Who makes it?

Merial

Merial

Merial

Merial

Active Ingredients

Fipronil
(S)-Methoprene

Fipronil

(S)-Methoprene

Pyriproxyfen

Afoxolaner

Afoxolaner

Milbemycin oxime

Kills fleas

Yes

Yes

Yes

Yes

Repels Fleas

No

No

No

No

Kills Flea Eggs and Larvae

Yes

Yes

No

No

Kills Ticks

Yes

Yes

Yes

Yes

Repels Ticks

No

No

No

No

Heartworm Protection

No

No

No

Yes

Other Parasites

Kills chewing lice

Kills chewing lice
Effective control for sarcoptic mange


Roundworm, hookworm, whipworm

Waterproof

Keep dry for 24 hours after application. Weekly bathing with soap can decrease effectiveness over time.

Keep dry for 24 hours after application. Weekly bathing with soap can decrease effectiveness over time.

Yes

Yes

How fast does it work?

Begins killing fleas within 4-12 hours of application, ticks within 24-48 hours of contact.

Begins killing fleas within 30 minutes of application, ticks within 24-48 hours of contact.

Active within 24 hours of application, fleas die within 4-8 hours of biting, ticks can take 24-48 hours to die after biting

Active within 24 hours of application, fleas die within 4-8 hours of biting, ticks can take 24-48 hours to die after biting

How often to dose?

Monthly

Monthly

Monthly

Monthly

How to give it?

Topical drops

Topical drops

Oral chewable tablet

Oral chewable tablet

Prescription required?

No

No

Yes

Yes

Age/Weight restrictions

Puppies 8 weeks and older

Puppies 8 weeks and older

Puppies at least 8 weeks old, weighing 4+ pounds

Puppies at least 8 weeks old, weighing 4+ pounds


NexGard Ingredients

There are two main lines of products that go under the name of NexGard. Their active ingredients are listed below:

NexGard®: Afoxolaner

NexGard Spectra®: Afoxolaner and Milbemycin oxime

Afoxolaner: This chemical is an insecticide and acaricide (which means it also kills ticks) that belongs to the isoxazoline family of chemicals. It works by blocking channels in the central nervous system of insects, while thought to be inactive in mammals.

Essentially, once ingested in small doses by the flea or tick when they bite your pet, this chemical scrambles their nervous system until they die.

There is not a lot of longitudinal data, or much understanding of potential environmental effects, of this chemical since it is pretty new on the scene. Merial, the company that makes NexGard, released it in 2013 after studies demonstrated its effectiveness and safety for use in dogs.

After a strong response from readers on her blog citing multiple problems after using these products, Veterinarian Elizabeth Carney used the Freedom of Information Act to request Adverse Drug Event reports from the FDA on Afoxolaner and a related drug fluralaner. You can read the report here.

We are providing this for information because we thought it might be helpful for our readers. However, do keep in mind that these are only reports of problems, not reports of safe use, so it is impossible to tell from this data how widescale any of these side effects may be.

Milbemycin oxime: This chemical is known to be a broad spectrum antiparasitic and it has long been used for the control of parasites in the nematode family (worms) as well as some mites such as sarcoptic and demodex mange. It is the active ingredient in common heartworm preventatives, such as Interceptor®.

If your dog is already on a heartworm medication, they will likely be taken off of that medication before starting NexGard.


NexGard Price

Depending on if you go for the NexGard (for fleas and ticks) or NexGard Spectra® (for fleas, ticks and heartworm protection) you will pay a little more for this than you will for Frontline options.

It is often sold at about twice the price of Frontline, but since Frontline may be losing some efficacy in some geographical regions, your vet may recommend this option for stronger protection for your pet.


NexGard Side Effects

According to the manufacturer, the most common side effects of this medication are vomiting, itching, diarrhea, lethargy and lack of appetite. In rare cases, it can cause seizures.

It should be noted that the safety of Nexgard for pregnant or lactating females has not been evaluated. In addition, this product should not be used with any dog that has a history of seizures.


How fast does NexGard work?

The active ingredient in Nexgard takes about 24 hours before it works its way through the system and becomes effective. Once that happens, it works only after the flea or tick bites your dog, and fleas die within 4-8 hours of biting, while ticks can take 24-48 hours to die.


NexGard: Pros and Cons

PROS
  • NexGard Spectra® has added heartworm protection that Frontline doesn’t have.
  • NexGard products may be more effective at flea and tick control in certain geographical regions. Ask your veterinarian which flea and tick preventatives are most effective in your area.
  • Oral dosing is less messy than topical treatments, and it won’t be made less effective by bathing or swimming.
  • Oral flea and tick prevention may be more environmentally sound since it wont wash off in rivers and streams. Too soon to call for sure though. However, it is definitely less likely to cause accidental exposure to children than topical treatments.
CONS
  • Fleas and ticks need to bite your dog in order for the poison to take effect.
  • If your dog happens to have a reaction to the active ingredients in these oral medications, there is no way to remove the drug from their system, unlike topicals which can be washed off using detergent soaps.
  • Since it is relatively new on the market, there are not good longitudinal studies about the safety of these kinds of oral flea and tick preventatives, causing some owners to pause with concerns about long term safety.
  • A fair bit more expensive than Frontline products.
  • Prescription required.

Frontline Ingredients

There are currently two main Frontline products on the market and they have different active ingredients. Let’s look at them both:

Frontline Plus Ingredients: Fipronil, (S)-Methoprene

Frontline Gold Ingredients: Fipronil, (S)-Methoprene, Pyriproxyfen

As you can see, Frontline Gold has an additional ingredient, but otherwise the formulas are the same. Here is the breakdown of each ingredient and how they work.

Fipronil: Fipronil is an insecticide that is part of the phenylpyrazole family. It was developed French company Rhône-Poulenc and released to the public in 1993. It works by blocking key pathways in the central nervous system of insects and causing them to essentially lose control over nervous system and muscles until they die, usually in as little as 4 hours of exposure.

It has been widely used for pest control in a variety of applications beyond pet flea and tick control. It has been used internationally for insect control in various agricultural applications where it is sometimes applied in huge quantities over large tracts of farmland or used to treat seeds before planting.

Due to growing concerns about the global loss of honey bees, a key pollinator for human foods, as well as a 2017 large scale contamination of eggs making their way into grocery stores, the use of fipronil in agricultural applications has been outlawed by the EU.  Honey bee colony collapse as a result of low dose fipronil poisoning has also been documented in the United States, although the Environmental Protection Agency’s actions remain weak in comparison to it’s European counterparts.  

Although it is thought that the drug works because it readily binds to GABA receptors in insects, but not as readily in animals, the drug is still moderately toxic if eaten in large quantities by people. Some other animals, such as rabbits, appear to be very sensitive to this chemical. It is widely known to be extremely toxic to fresh water and marine environments, and aquatic non-vertebrates in particular.

There is a growing body of anecdotal evidence that fipronil is losing its potency for flea control in some geographic regions, likely due to the widescale use of this product and the (inevitable) resistance developed by fleas to the poison.

Despite rampant experiences with the failure of once effective flea and tick treatments by owners that have been using them for years, and many veterinarians noting fluctuation in the effectiveness of certain products in their region, the issue of fleas developing resistance is a matter of controversy in scientific quarters where the lack of effectiveness of products is often dismissed as owner error.

(S)-Methoprene: This chemical is part of a family of methoprene derivatives that mimic a naturally occurring hormone that is associated with signaling juvenile growth states. In other words, when this chemical is present, it tricks the biological system of insects in the pupa stage to remain in that stage, effectively interrupting the life cycle, and preventing the pupa from growing into adult parasites.

In terms of fleas, this chemical has a powerful effect in terms of stopping an infestation in its tracks. It has also been widely used for mosquito control in areas where they cause outbreaks of malaria, West Nile Virus, Zika Virus and other diseases.

The EPA considers Methoprene to be safe for humans and other non-target species and has exempted it from regulation in food. However, it has been shown to be mildly toxic to some fish where it can accumulate in their tissues. Recent research has also shown it is toxic to crustaceans such as shrimp and lobster as well as amphibians, such as frogs and salamanders. It has been shown to be extremely toxic to many freshwater invertebrates.

Although largescale resistance to Methoprene in flea populations has not been documented, there is some evidence to suggest that mosquitos may be developing resistance to this class of pesticide.

Pyriproxyfen: This ingredient found in Frontline Gold (but not Frontline Plus) is another Insect Growth Regulator that works by tricking the biological mechanisms of insect larva into not developing into adults, thus interrupting the life cycle.

It was first developed in 1996 as an insecticide used against the white fly, a major pest of cotton crops. It is now used in a variety of insect control products used to treat household infestations such as cockroaches and ants.

In the largest scale mosquito control efforts in human history, Brazil added Pyriproxyfen to the human water supply in 2014 in an effort to control mosquitos responsible for a massive Zika outbreak plaguing the country. The virus is widely suspected of causing microcephaly, a major birth defect, when it infects pregnant women.

There was a subsequent controversy that ensued, with some researchers claiming that pyriproxyfen itself might have been the cause of the very high incidents of microcephaly that had surged in the region not long after they chemical was added to the water supply. Studies comparing the incidents of microcephaly in geographic regions affected by Zika with and without the water treatment, also question the role of the pesticide in these birth defects.

Although dismissed by authoritative sources such as the World Health Organization and the European Union, some organizations such as the Brazilian Association of Collective Health remain skeptical about the wide scale addition of this insect growth regulator to the water supply. Brazil has currently stopped the use of this chemical in the human water supply.


Frontline Price

Frontline is the more economical choice when you compare NexGard and Frontline. However, it may not be as effective, depending on your geographical region, because of potential pesticide resistance to this older drug. Although it does not require a prescription to buy, you should talk to your vet to make sure these products will be effective in your area.


Frontline Side Effects

Hair loss and/or mild irritation at the site of application is one of the most common side effects of this product. If it lasts more than a few days and/or gets very irritated looking, definitely get in to see your veterinarian.

In some rare cases, some dogs may be hypersensitive to the ingredients in Frontline and have serious reactions to it. Contact your vet immediately if your dog experiences more serious side effects such as a noticeable change in personality, loss of coordination, swelling of the face, seizures, vomiting, diarrhea or a change of appetite lasting more than 24 hours.


How fast does Frontline work?

Although it can take up to 24 hours for the product to distribute evenly over your dog’s skin, once it has done that it takes roughly 4-12 hours to kill fleas and ticks within die 24-48 hours of contact. Notably, the active ingredients kill on contact so these parasites do not even have to bite in order for the poison to take effect.

Frontline products also contain insect growth regulators designed to keep eggs and pupae from developing into adult fleas, thus stopping the lifecycle of these nasty critters. This is especially important if you are dealing with an infestation of fleas.


Frontline Pros and Cons

PROS
  • Does not require a prescription.
  • Kills on contact, versus NexGard which requires fleas and ticks to bite first.
  • Usually less expensive than NexGard products.
  • Kills fleas and ticks on contact with the product, no biting necessary for it to be effective.
  • Does not require ingestion. If your dog happens to have a reaction, you will be able to get it off to stop the reaction.
CONS
  • Fleas in some regions of the country may have developed a resistance to the active ingredients in Frontline Plus. Talk to your vet to find out what is working best in your area.
  • Does not include heartworm protection in either line, unlike NexGard Spectra®.
  • There are some fairly serious environmental concerns about using insect growth regulators since they have been implicated in honey bee colony collapse syndrome and are potentially dangerous to aquatic life.

NexGard and Frontline: Which is safer?

While Frontline and NexGard have both been tested and approved for use for dogs, you may have read on the internet that they are unsafe and can lead to seizures and even death in some dogs.

Keep in mind that literally millions of our pets are safely using these medications, so even hundreds of dogs experiencing rare side effects is statistically a very small number, even though the stories are very difficult to read.

In terms of which is safer, we did not find any research to confirm if either of these products is safer than the other, although it is fair to say that the active ingredients in Frontline have been used for a longer time frame, thus there is more data to support their safe use.

In addition, Frontline is topical which gives you the advantage of getting it off of your dog should they have an adverse reaction. Since NexGard is oral, once it is in your dog’s system, you will have to ride out any side effects until the medication wears off (in a month).

On the other hand, widespread reports that some regions now have fleas that have become resistant to the active ingredients in Frontline, while not scientifically proven, may make Frontline less effective in your particular area, a safety concern when it comes to flea infestations in some climates. Talk to your vet to be sure if Frontline will be effective in your neck of the woods.

If you would like to try more natural flea and tick preventatives, be sure to check out our informative article on the best flea and tick shampoos, several of which use natural flea and tick killing and repelling essential oils instead of pesticides.


Which is better? Frontline vs. Nexgard

This is a question we can’t answer for you. Unfortunately, the answer is different depending on your location, your dog’s specific health history, and other factors that keep us from making a call either way.

What we suggest is that you work closely with your vet to develop the right flea and tick prevention strategy for your pet.

Keep good records of when you use these products and follow the instructions for dosing and applications carefully. If you notice any side effects, talk with your vet.


Nexguard and Frontline together?

NEVER MIX FLEA AND TICK PRODUCTS. This is such an important rule to follow that we decided to yell it.

The active ingredients in flea and tick products are designed to work as directed, and their toxicity has been studied at certain doses. In addition, many of these medications use different chemicals but act in similar ways, meaning they can have a synergistic effect that is toxic.

If you are using a topical treatment, do not also give your dog an oral treatment. If you are using a spray, do not also use a powder. If you are using a collar, don’t also use the topical drops. Just do not ever mix these products!


Conclusion: Frontline or Nexgard?

We hope this article has helped you learn more about NexGard verses Frontline so that you can work with your vet to chose the flea and tick prevention strategy that is right for your dog.

Do you have a favorite? We love to learn about the experiences our readers are having so feel free to drop us a line and comment below. Let’s get a productive conversation going about which of these products are working for you and your pets.

Let us know your geographical region too…since that might help others in your area find the products working best in your area.

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