Bravecto, Nexgard, or Other: Which Oral Flea Control Should You Use?
Get updated on the side effects, safety, and methods of the most widely prescribed flea-killing medications for dogs on the market.
Note: Since this article came out in the September issue of Whole Dog Journal, we have received a number of reader comments expressing concern over the fact we might condone the regular practice of feeding oral flea medications to our dogs. Perhaps our standard caveats weren’t strong enough: We always promote simple, safe, and natural solutions for our dogs’ health, training, and behavior before promoting chemical (or toxic) answers to their wellness needs. But, as we have from our beginning 20 years ago, we aren’t so hard over on the natural wellness route that we dismiss out of hand all mainstream or veterinarian-prescribed treatments to our dogs' most vexing problems.
There’s no getting around the fact that the most common trigger for allergic reactions in dogs is flea bites. Flea allergy dermatitis is so common, in fact, that if your dog is persistently itchy, your veterinarian might not be willing to even consider any other potential cause of his itching until your dog has been maintained on whatever flea-prevention treatment your veterinarian approves of for at least a few months! If your veterinarian takes this position, and if you consent, then you’ll have to make some choices about which oral flea medication to use.
We hope this comparison article will serve as a guide if you and your veterinarian decide oral flea medication vs. topical is the best way to eradicate these parasites. If you do, make sure you read the fine print regarding contraindications: that is, whether or not your dog’s pre-existing conditions or medications might preclude her from taking oral flea meds. More on that below.
Keep in mind that a decision to use one of these drugs needn’t be “forever”. We feel they should be used for only as long as it takes to get the flea population in your home under control. Then, alert surveillance and routine cleaning should be enough to keep fleas at bay.
It begins with a simple itch.
If a dog is particularly itchy – and especially if he’s focusing on itchy places such as his flanks and his back at the top of his tail – the first thing to suspect is that he’s been bitten by fleas, or maybe even just one flea. All dogs itch when bitten by fleas, because flea saliva, which is injected into your dog when the flea bites and feeds on your dog’s blood, is irritating. But dogs with an allergy to flea saliva may go berserk with pruritus (severe itching), chewing and scratching themselves until a hot spot (formally known as acute moist pyotraumatic dermatitis) forms.
Today, there are any number of tools and tactics an owner can employ to eliminate fleas as a source of her dog’s discomfort. These include:
- Oral medications
- Topical “spot-on” pesticides
- Insect growth regulators (IGRs), which prevent the normal development of flea eggs and larvae
- Other topical pesticides: shampoos, dips, powders, sprays
- Treatments for the dog’s environment
- Cleaning methods aimed at ridding/killing non-adult fleas
- An approach that encompasses several or all of these would be called integrated flea control, or more generally, integrated pest management
For several reasons, veterinarians tend to put the most stock in the first two on this list – and more specifically, the prescription-only versions of these. In fact, these are the two most effective solutions for killing fleas – but they aren’t without potential side effects and they should represent only a part of a dog owner’s efforts to control fleas.
This month, we’ll examine the prescription oral flea-control medications that kill adult fleas. In the October 2017 issue, we’ll discuss prescription oral medications that help control fleas through the use of insect-growth regulators, as well as the over-the-counter oral products that kill fleas. In later issues, we’ll survey the spot-on pesticides and other flea-control strategies.
Why Choose Oral Flea Medication Over Topical?
Last year, I fostered a Great Dane who had a very thin coat and who was very itchy. When I took her to a veterinarian for a complete examination and discussion of what we could do for her itching, the vet essentially refused to consider any sort of allergy diagnosis or treatment until the dog had been on an oral flea-prevention medication for a minimum of three months. She said, that in her opinion and experience, “only longer-term oral medications offer enough protection from fleas to rule out an allergy to fleas as the cause of persistent itching.” To that end, she prescribed a medication called Bravecto, a drug that can kill any fleas that bite the dog for as long as 12 weeks after the dog is dosed.
I countered that I could repeat topical insecticides at regular intervals. But the veterinarian was firm in her belief that only a dose of Bravecto would ensure that there would be no gap in flea prevention for long enough to ensure that the Dane’s itching was not caused by fleas.
Merck, the maker of Bravecto, strongly promotes this point, taking slightly different tacks on its product website pages for owners and veterinarians. Owners are told that Bravecto makes flea control easy: “With Bravecto Chew, dogs get 12 weeks of flea and tick protection with a single treatment. That’s nearly three times longer than monthly treatments. This makes it easy for you to provide long-lasting coverage to your dog, without having to worry about remembering frequent treatments.”
On Merck’s pages for veterinarians, the most-promoted benefit is owner compliance: “Convenient long-lasting protection means less chance of noncompliance,” it says on one page. “Bravecto makes all the difference in improving pet-owner compliance,” it says on another.
Advantages of Edible Flea Medication
There are a number of other advantages to using an oral flea-control product:
If you or your children pet the dog, you may prefer not to have contact with a topical product. This could also be true in a multi-pet household where pets groom each other.
Dogs with longer coats often sport a “greasy spot” for several days after topicals have been applied, increasing the concern of petting the dog and coming into contact with the pesticide.
Owners of dogs with skin problems, or who have had a reaction in the past to any sort of topical product, might prefer to use an oral one.
Bathing or even swimming too soon after application may reduce the effectiveness of topicals.
Some ingredients used to kill ticks, such as permethrin (used in K9 Advantix and other products) and amitraz (used in Certifect and the Preventic collar), are toxic to cats, which can be a problem in a household that includes both, especially if they are friendly with each other. In that case, giving the dog an oral product would be safer for the cat.
Because the insecticides in the newer oral products haven’t been used for very long, they can be more effective in areas where fleas and ticks may have built up some resistance to the older topical products.
Last but not least, oral flea-control medications have been proven to be more effective than topical pesticides in both killing fleas and helping to control a household infestation more quickly.
Every product you feed or use on your dog poses some amount of risk, and some percentage of dogs will react badly to any product.
One disadvantage of these medications is that, once a dog digests one, it’s in his system for as long as it’s designed to be. If a dog has an adverse reaction to a topical pesticide, his owner can immediately bathe him to reduce the adverse effects. The effects of an oral medication can’t be mitigated in this way.
That said, the most common adverse side effects of oral flea-control medication are stomach upset and vomiting. The very fact that a dog can vomit up the medication – and the possibility that he might do so without you being aware of this – is a fairly significant disadvantage, too. If you don’t find the vomit, you may think the product was just plain ineffective. And then there is the possibility the vomit is discovered and eaten by another one of your dogs!
It should also be noted that while all of these products are formulated with palatants to entice a dog to chew them up and eat them, some dogs may refuse. In this case, you will be forced to either sneak the medication into the dog’s food or give it to him like any other pill – and you’d have to break the larger doses for large dogs into pieces to “pill” them.
It should be noted that an oral medication can compromise the integrity of a necessarily strict food-allergy trial.
Only a very small percentage of dogs suffer the most serious adverse reactions posed by this class of medication: seizures and other neurological reactions.
Types of Oral Flea Control Products for Dogs
There are several types of oral products that are marketed to dog owners to help with flea infestations:
1. Prescription oral flea-killing medications. These work in the dog’s system for at least a month.
2. Over-the-counter (OTC) oral flea-killing medications (Capstar, Capguard, FastCaps, Advantus). None of these products work for longer than 24 hours – but they do work quickly to kill fleas.
3. Prescription medications that do not kill fleas, but contain insect-growth regulators, which help control flea populations by preventing the fleas from maturing and reproducing (Sentinel, Sentinel Spectrum). Fewer adverse reactions in dogs are reported for these products than for the flea-killing medications.
Again, this month, we’re going to discuss only the prescription oral flea-killing medications. We’ll look at the other two categories next month.
Prescription Oral Flea-Killing Medications
|PRODUCT||EFFECTIVE AGAINST||CHEMICAL CLASS||ACTIVE INGREDIENT||FREQUENCY||EFFICACY||DATE OF FDA APPROVAL||MIN. AGE AND WEIGHT|
|Fleas, ticks, demodex*||Isoxazoline||Fluralaner||Up to 12 weeks||>98% of fleas and 100% of ticks within 12 hours||2014||6 months, 4.4 lbs.|
(888) 637-4251 (opt 3)
|Fleas, ticks, demodex*||Isoxazoline||Afoxolaner||Monthly||100% of fleas within 24 hours (no claims made for ticks)||2013||8 weeks, 4 lbs.|
|Fleas, ticks, demodex*, scabies* ear mites*||Isoxazoline||Sarolaner||Monthly||Starts within 3 hours for fleas, 8 hours for ticks||2016||6 months, 2.8 lbs.|
|Fleas||Spinosyn||Spinosad||Monthly||100% of fleas within 4 hours||2007||14 weeks, 3.3 lbs.|
|Fleas, heartworms, roundworms, hookworms, whipworms||Spinosyn||Spinosad, milbemycin oxime||Monthly||100% of fleas within 4 hours||2011||8 weeks, 5 lbs.|
|*Not yet approved in the U.S. for control of these parasites, though veterinarians might suggest them as “off-label” treatments.|
There are not that many medications approved by the FDA for controlling fleas on dogs. Most products contain one significant “active ingredient” that controls fleas, although a few contain more than one.
The newest class of insecticides are isoxazolines, chemicals that are selectively toxic to insects (fleas) and acarines (mites and ticks) in a way that does not pose a risk to mammals. Isoxazolines kill fleas and ticks by inhibiting their ligand-gated chloride channels, in particular, those gated by the GABA neurotransmitter. This blocks pre- and post-synaptic transfer of chloride ions across cell membranes, resulting in uncontrolled activity of the fleas’ and ticks’ central nervous system (CNS) and death.
In plain English? The operation of many physiological processes rely on ion channels, chemical pathways where charged ions from dissolved salts (including sodium, potassium, calcium, and chloride) pass through otherwise impermeable cell membranes. Most of these channels are gated, opening and closing in response to certain stimuli. Isoxazolines close the chemical gates on chloride channels that are essential for the CNS of fleas and ticks, resulting in their death.
The active ingredient in NexGard, a product introduced by Frontline Vet Labs, a division of Merial, Inc., in 2013, is an isoxazoline chemical called afoxolaner. It is given once a month. Each NexGard treatment kills fleas and the black-legged tick, American dog tick, Lone Star tick, and brown dog tick. It also kills the mite responsible for demodectic mange, though it has not yet received FDA approval for this use.
Studies indicate NexGard was 100 percent effective against fleas within 24 hours, and more than 97 percent effective against American dog ticks and Lone Star ticks, 94 percent effective against black-legged ticks, and 93 percent effective against brown dog ticks.
NexGard can be given with food or on an empty stomach.
The most common adverse reactions recorded in clinical trials were vomiting, itching, diarrhea, lethargy, and lack of appetite.
Nexgard is said to be safe for dogs and puppies who weigh four pounds or more and who are at least eight weeks of age. No adverse reactions were observed in preapproval studies when NexGard was used concomitantly with other medications, such as vaccines, dewormers, antibiotics, steroids, NSAIDS, anesthetics, and antihistamines. The safe use of NexGard in pregnant, breeding, or lactating dogs has not been evaluated. Use with caution in dogs with a history of seizures.
The active ingredient in Bravecto, a product introduced by Merck Animal Health in early 2014, is an isoxazoline chemical called fluralaner. It is given once every three months. Each Bravecto treatment kills fleas and certain species of ticks (black-legged tick, American dog tick, and brown dog tick) for 12 weeks, three times longer than any other oral flea treatment. It kills the lone star tick for eight weeks. It also kills the mite responsible for demodectic mange, though it has not yet received FDA approval for this use. Studies indicate that Bravecto kills more than 98 percent of fleas, and 100 percent of ticks, in less than 12 hours after administration.
Bravecto should be administered with food to maximize the bioavailability of the active ingredient.
The most common adverse reactions recorded in clinical trials were vomiting, decreased appetite, diarrhea, lethargy, polydipsia (excessive drinking), and flatulence.
Although its maker offers no specific warning about this in its product literature, Bravecto should be used with caution in dogs with a history of seizures, similar to other drugs in this class.
Bravecto is said to be safe for pregnant, breeding, and lactating dogs, dogs weighing at least 4.4 pounds, and for puppies who are at least six months old (and 4.4 pounds). No adverse reactions were observed in pre-approval studies when Bravecto was used concurrently with other medications such as vaccines, de-wormers, antibiotics, and steroids.
The active ingredient in Simparica, a product introduced by Zoetis in 2016, is an isoxazoline chemical called sarolaner. It is given once every month. Each Simparica treatment kills fleas (100 percent within 24 hours) and certain species of ticks (almost 97 percent of Lone Star tick, Gulf Coast tick, American dog tick, black-legged tick, and brown dog tick) for one month.
Simparica also kills the mites responsible for demodectic mange (demodex), sarcoptic mange (scabies), and otodectic mange (ear mites), though it has not yet received FDA approval for these uses. (We’ve seen reports from veterinarians who are using it for this off-label use with great success.) Its claim to fame is its speed; Zoetis claims that Simparica starts killing fleas within three hours and ticks within eight hours of administration.
Simparica may be administered with or without food.
Simparica may cause abnormal neurologic signs such as tremors, unsteadiness, and/or seizures. Simparica has not been evaluated in dogs who are pregnant, breeding, or lactating. Simparica has been safely used in dogs treated with commonly prescribed vaccines, parasiticides and other medications. The most frequently reported adverse reactions were vomiting and diarrhea.
Simparica is said to be safe for dogs weighing at least 2.8 pounds, and for puppies who are at least six months old (and 2.8 pounds).
This class of chemicals does not kill ticks, only fleas. Spinosyns work in a similar fashion as the isoxazolines, in that they activate reactions in the flea’s cellular ion channels (in this case, the nicotinic acetylcholine receptors or nAChRs), causing a fatal CNS reaction in the fleas. Insects treated with spinsyns show involuntary muscle contractions and tremors resulting from activation of motor neurons. Prolonged spinosad-induced hyperexcitation results in prostration, paralysis, and flea death. The selective toxicity of spinosad between insects and vertebrates may be conferred by the differential sensitivity of the insect versus vertebrate nAChRs.
The prescription oral flea-killing products in this class of medications all utilize a spinosyn called spinosad.
These products are the same thing; Elanco makes AcuGuard for the VCA chain of veterinary hospitals under the Vethical brand.
As previously mentioned, the active ingredient in Comfortis and AcuGuard is spinosad. These products were FDA-approved in 2007. They are given once every month. Each treatment kills fleas for one month. Flea count reductions of 97.9 percent were observed one month after the first treatment and 99.9 percent after three monthly treatments with Comfortis or AcuGuard.
Administer these products with food for maximum effectiveness.
The most common adverse reaction reported from Comfortis/AcuGuard is vomiting. Other adverse reactions reported in decreasing order of frequency are: depression/lethargy, decreased appetite (anorexia), incoordination (ataxia), diarrhea, itching (pruritis), trembling, excessive salivation, and seizures.
Following concomitant extra-label use of ivermectin (very high doses used to treat mange) with Comfortis/AcuGuard, some dogs have experienced the following clinical signs: trembling/twitching, salivation/drooling, seizures, incoordination (ataxia), excessive dilation of pupils (mydriasis), blindness, and disorientation. Products containing spinosad should be safe when used along with the normal heartworm preventive dosage of ivermectin or milbemycin oxime, but use with caution in dogs who have or may have the MDR1 mutation that causes sensitivity to certain drugs. See “Dogs with the MDR1 Mutation: Drug Sensitivites,” (December 2012) for more information.
Neither should these products be combined with high doses of milbemycim oxime (Interceptor, Sentinel), used to treat demodectic and sarcoptic mange, as this combination can cause serious adverse neurological effects.
While Elanco says these products can be combined with other flea and tick products, we wouldn’t recommend it. Nor should Comfortis/NexGuard be used for dogs with epilepsy or other seizure disorders.
Use with caution in breeding females. The safe use of Comfortis/AcuGuard in breeding males has not been evaluated.
Comfortis/AcuGuard is approved for use in dogs 14 weeks of age or older and 3.3 pounds of body weight or greater.
These products are the same thing; Elanco makes ComboGuard for the VCA chain of veterinary hospitals under the Vethical brand.
Trifexis and ComboGuard combine spinosad with milbemycin oxime, a chemical that is used as a heartworm-preventive and is effective against intestinal parasites (hookworms, roundworms, and whipworms).
Trifexis/ComboGuard is approved for use in dogs and puppies eight weeks of age or older and five pounds of body weight or greater.
Administer these medications with food for maximum effectiveness.
Treatment with fewer than three monthly doses after the last exposure to mosquitoes may not provide complete heartworm prevention. Prior to administration of Trifexis/ComboGuard, dogs should be tested for existing heartworm infection. Use with caution in breeding females. The safe use of these medications in breeding males has not been evaluated.
Use with caution in dogs with pre-existing epilepsy.
What Elanco calls “mild, transient hypersensitivity reactions manifested as labored respiration, vomiting, salivation, and lethargy” have been noted in some dogs treated with milbemycin oxime carrying a high number of circulating heartworm microfilariae. These reactions are presumably caused by release of protein from dead or dying microfilariae. Milbemycin oxime is more effective against microfilariae than most other heartworm prevention medications (including ivermection) and may therefore cause anaphylaxsis if given to a heartworm-positive dog.
Just as with Comfortis and AcuGuard, following concomitant extra-label use of ivermectin with spinosad, some dogs have experienced the following clinical signs: trembling/twitching, salivation/drooling, seizures, incoordination (ataxia), excessive dilation of pupils (mydriasis), blindness and disorientation. Spinosad alone has been shown to be safe when administered concurrently with heartworm preventatives at label directions.
Again, products containing spinosad should be safe when used along with the normal heartworm preventive dosage of ivermectin or milbemycin oxime, but use with caution in dogs who have or may have the MDR1 mutation that causes sensitivity to certain drugs.
The most common adverse reactions reported are vomiting, depression/lethargy, itching (pruritic), decreased appetite (anorexia), diarrhea, trembling/shaking, ataxia, seizures, hypersalivation, and skin reddening. Puppies less than 14 weeks of age may experience a higher rate of vomiting.
Tips for Safe Flea Medication Use
1. Read the medication directions before giving to your dog.
Always read the instructions for use carefully before administering to your dog, especially the cautions and contraindications. It’s always shocking when we hear that someone gave their dog a medication without reading the instructions – and often refusing to take responsibility. “My veterinarian prescribed it! How was I supposed to know it could make my dog sick?” While it’s true that a veterinarian should inform her clients about the contraindications of any product she recommends, in reality, few vets have or take the time. If you read something in the product insert’s cautions and contraindications that seems like it would apply to your dog and concerns you, call your veterinary hospital and ask for the vet to call you back to discuss it – again, before you give the product to your dog.
2. Pay attention to the instructions.
Always follow the directions carefully. Products for cats and dogs are not interchangeable; a number of products for dogs are potentially fatal for cats. Topical products should not be ingested. Pay special attention to weight and age minimums for safe use, as well as the cautions regarding administration to sick, weak, old, medicated, pregnant, or nursing dogs.
3. Observe your dog carefully after administering a flea-control medication.
Most adverse reactions happen within a few hours. Contact your veterinarian with a speed that is congruent with the seriousness of your dog’s symptoms. (Serious? Go the to veterinary ER! Mild? Call your vet the next day to report and ask the staff to note this in your dog’s chart.)
4. Treat every pet.
It’s important to treat all dogs and cats in a household. Fleas can reproduce on untreated dogs and cats and allow infestations to persist.
5. Start a flea control calendar.
Keep track of when you administer a flea-control product to your dog. It’s advisable to write the date, time, product, and dosage on a calendar that you can easily refer to if your dog has an adverse reaction and you need to recount details to your veterinarian. Also note any abnormalities you may notice in your dog’s health, appetite, digestion, and demeanor after administration.
Nancy Kerns is the editor of WDJ.