When to Use Trifexis vs Sentinel for Dogs Which Preventative Is Right for Your Pet?

When to Use Trifexis vs Sentinel for Dogs
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Fleas and ticks and their other pest friends are not only gross, but annoying to both pets and pet parents. Find out more here about two preventative medications that stop these horrible little creatures in their tracks.

What are the differences that emerge when comparing Trifexis vs Sentinel for dogs? These popular preventatives are comparable in many ways, including price. Both medications are administered orally to keep parasitic worms, including heartworms, at bay. Both medications treat fleas -- one at the egg stage and one at the adult stage. And both medications are administered orally, in the form a flavored chewable tablet. So which one is better for your dog?


Both drugs protect against heartworm, hookworm, roundworm, and whipworm.

  • Sentinel interrupts the flea life cycle by ensuring that female fleas who feed on treated animals will produce eggs that cannot hatch.
  • Trifexis also addresses fleas, by killing adult fleas.
  • Neither drug protects against ticks.
  • Both drugs are a good alternative to monthly spot-on topical treatments for dogs who have sensitive skin, or in cases where spot-ons are not practical because children or other animals in the home may have contact with topicals while they’re still wet.


Both medications are to be administered orally once a month, and will last for 30 days.


  • The primary ingredients in Trifexis are spinosad and milbemycin, which both have very low rates of toxicity in mammals.
  • Sentinel also contains milbemycin. Its second ingredient is lufenuron, which is primarily non-toxic to dogs, though it can sometimes be irritating to the stomach.
  • These are, by and large, safe drugs, with one exception. Milbemycin should not be given to Collies or other herding dogs. These breeds have a known intolerance for this drug.


Sentinel should not be given to puppies ‘till they’re at least 4 weeks of age, or 2 lbs. Trifexis should not be administered until puppies are 8 weeks of age, and 5 lbs.


The effects of both drugs on pregnant and lactating dogs have not been evaluated.


Lufenuron (in Sentinel) protects against both heartworms and fleas by attacking a naturally occurring glucose derivative found in the bodies of insects, called chitin. Neither dogs or humans require chitin to live, but fleas and certain intestinal worms need chitin to grow and live. Lufenuron attacks the chitin in these parasites, which -- in the case of fleas -- prevents them from ever developing an exoskeleton. In the case of worms, it attacks worms at the cellular level, preventing them from developing.

Spinosad (in Trifexis) kills adult pests through “hyperexcitation” of the nervous system. This is why dogs may appear itchy or restless in the first hour or so after taking the drug. Adult fleas may be especially active on their skin before falling dead from drug-induced nervous breakdowns!



For the Prevention of...

Recommended age of application


Oral tablet, once a month.

Heartworm, hookworm, roundworm, whipworm, and adult fleas.

6 weeks or older


Oral tablet, once a month.

Heartworm, hookworm, roundworm, whipworm, and fleas at the larval stage.

4 weeks or older, 2 lbs or larger

Is Trifexis the best for dogs?

Trifexis is a well-known and frequently prescribed oral drug for dogs that offers defense against several parasites, including fleas, heartworms, hookworms, roundworms, and whipworms. Even though it is a reliable product and has worked for many dogs, it is important to remember that what constitutes "the best" might differ based on the circumstances of each dog, such as their health, way of life, and particular parasite issues. Trifexis is well-liked because of a number of benefits. First of all, it provides a practical all-in-one remedy, doing away with the requirement for many treatments to treat different parasites. For pet owners, this makes the administrative process simpler. Second, Trifexis has proven effective against a variety of parasites, providing dogs with total protection. The medication's once-monthly dosing also makes it simple to work it into a regular schedule. In all, Trifexis may be considered one of the best anti-parasitic oral medications available for pets.

Is Sentinel a good flea medicine for dogs?

Yes, Sentinel is a good flea medication for canines. It is a well-known and reliable canine flea treatment that offers full defense against fleas as well as other parasites including heartworms, hookworms, roundworms, and whipworms. Despite being a popular choice for many dogs, Sentinel's appropriateness as the "best" flea treatment depends on a number of characteristics that are unique to each dog. Milbemycin oxime and lufenuron are two essential components of Sentinel, which distinguishes it for its distinct method of action. The broad-spectrum parasiticide milbemycin oxime kills heartworm larvae as well as other common intestinal worms. On the other hand, lufenuron functions differently by preventing the development of flea eggs, thus disrupting the flea life cycle. This two-way system offers a multifaceted strategy for flea control. Sentinel's simplicity of administration is one of its benefits. It comes in the shape of a flavor-infused tablet, which dogs often enjoy. For pet owners, this makes dosing simple and convenient. Sentinel must also be prescribed by a veterinarian who can evaluate the dog's unique needs and determine the right dosage because it is a prescription drug. It is significant to remember that while Sentinel successfully prevents flea infestations, it does not instantly eliminate adult fleas. Therefore, extra measures like a quick-acting adulticide may be required if a dog already has a serious flea infestation in order to handle the condition.

Is Sentinel safer than Trifexis?

Sentinel and Trifexis are both popular and widely used medications for dogs that provide protection against various parasites. In terms of safety, both products have undergone rigorous testing and are considered safe when used according to the manufacturer's instructions. You should note that individual dogs may react differently to medications, and what is safe for one dog may not be for another. While both Sentinel and Trifexis have a similar safety profile, they contain different active ingredients. Sentinel contains milbemycin oxime and lufenuron, while Trifexis contains spinosad and milbemycin oxime. Each of these ingredients has its own specific safety profile. It is recommended to consult with a veterinarian to determine the most suitable and safe option for a particular dog, taking into consideration factors such as the dog's health history, any known allergies or sensitivities, and any medications the dog is currently taking. However, unlike Sentinel, Trifexis has not yet been studied for use in breeding, pregnant, or nursing dogs. These dogs can safely use Sentinel.

What is the difference between Trifexis and Sentinel Spectrum?

Both Trifexis and Sentinel Spectrum are oral drugs intended to prevent parasites in dogs. However, they differ significantly from one another. Trifexis gives defense against fleas, heartworms, hookworms, roundworms, and whipworms and contains the active components spinosad and milbemycin oxime. It offers thorough parasite control due to its wide spectrum coverage. On the other hand, the active components of Sentinel Spectrum are milbemycin oxime, lufenuron, and praziquantel. Sentinel Spectrum offers defense against tapeworms in addition to fleas, heartworms, and intestinal worms (hookworms, roundworms, and whipworms). However, Sentinel Spectrum stands out for its added protection against tapeworms, which makes it a good option for dogs who are more likely to develop tapeworm infestations. Their methods of action also differ. Trifexis, which contains the active components spinosad and milbemycin oxime, controls intestinal parasites in addition to killing fleas and preventing heartworm illness. Sentinel Spectrum prevents heartworms, manages intestinal worms, and disrupts the flea life cycle by preventing the production of flea eggs. It also contains milbemycin oxime, lufenuron, and praziquantel. This indicates that Sentinel Spectrum concentrates on avoiding flea infestations by targeting flea eggs, whereas Trifexis kills existing fleas.

Will Sentinel deworm my dog?

Yes, Sentinel works well to deworm dogs. Its active components, milbemycin oxime, and lufenuron, are designed to specifically target and get rid of common intestinal worms like whipworms, hookworms, and roundworms. Dogs who have these parasites may experience health hazards; thus, routine deworming is a crucial component of their overall care.

More on Pest Control

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This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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