Hepper is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

Trifexis vs Sentinel: We Asked a Vet

Dr. Rebecca MacMillan (Vet) Profile Picture

By Dr. Rebecca MacMillan (Vet)

Trifexis vs Sentinel - ft

Review Summary

We all want what’s best for our pets, whether that’s a good quality diet, the latest interactive toy, or effective parasite control. But where do you begin? With so many parasite treatments available it can be hard to know which one to give to our dogs. In this review, we explore two anti-parasite tablets, Trifexis and Sentinel.

Both products are flavored tablets, though Trifexis is a chewable one, which might make it more appealing for some dogs. They can both be hidden in food though, which is helpful.

What are they for?

Trifexis kills adult fleas, whereas Sentinel acts on preventing egg development, breaking the flea life cycle in an alternative way. This is fine as part of a preventative treatment program but could mean it might take a while for flea numbers to drop in the face of an outbreak. A separate adulticide product may be needed in some cases.

If you have a very young or small animal requiring treatment, then you will need to choose Sentinel as this can be safely used in puppies from as young as 4 weeks in age and 2 lbs in body weight.

Both products will require a prescription from a veterinarian so if you are unsure which product is best for your pet then you can discuss it with them. Ultimately though, the decision may be made by whichever product your veterinarian prefers and stocks in their clinic!

divider 10

At a Glance

trifexis vs sentinel
Image Credit: Left – Trifexis (Chewy); Right – Sentinel (Chewy)
Trifexis
  • Spinosad and milbemycin oxime
  • Licensed for use in dogs
  • Treats adult fleas, heartworm, adult hookworm, adult roundworm, and whipworm
  • Given monthly
  • Must be prescribed by a veterinarian
  • Chewable flavored tablet
  • Can be used in puppies aged 8 weeks and over
  • Discuss its use in breeding bitches with your veterinarian
  • Available in different tablet sizes for different body weights
Sentinel
  • Milbemycin oxime and lufenuron
  • Licensed for use in dogs
  • Treats immature fleas, heartworm, hookworms, roundworms, and whipworms
  • Given monthly
  • Must be prescribed by a veterinarian
  • Flavored tablets
  • Can be used in puppies aged 4 weeks and over
  • Safe to use at recommended doses in pregnant and nursing bitches
  • Available in different tablet sizes for different body weights

divider 9

Overview of Trifexis

Trifexis for dogs (40.1 - 60 lbs)
Image Credit: Chewy

Ingredients

Trifexis contains Spinosad and milbemycin oxime. Each chewable flavored tablet is formulated to provide a minimum Spinosad dose of 13.5 mg/lb (30 mg/kg) and a minimum milbemycin oxime dose of 0.2 mg/lb (0.5 mg/kg).

Indications

Trifexis is used to prevent heartworm disease (Dirofilaria immitis). It is also used to kill fleas and helps in the treatment and prevention of flea infestations. Trifexis also helps to both treat and control adult hookworm (Ancylostoma caninum), adult roundworm (Toxocara canis and Toxascaris leonina), and adult whipworm (Trichuris vulpis).

Dogs should be tested for the presence of heartworm before treatment with this product however, as an alternative product may be required to kill adult heartworm and microfilariae.

Instructions for use

Trifexis can be used in dogs and puppies aged 8 weeks and over, and that weigh at least 5 lbs.

Dosage

The tablets are given once a month by mouth. Giving it with food increases its effectiveness. Make sure the appropriate tablet size is used for your dog’s body weight. If your dog vomits within an hour of receiving the tablet, then he will need to be re-dosed.

The product can be given all year round at continuous monthly intervals to provide maximum protection.

Mechanism of action

Trifexis contains two active ingredients: milbemycin oxime and Spinosad.

Milbemycin oxime affects the nerve and muscle cells of insects, causing paralysis and death in parasites.

Spinosad activates nicotinic acetylcholine receptors in insects. This causes involuntary muscle contractions and tremors from the activation of motor neurons. This hyperexcitation results in paralysis and flea death. Trifexis, therefore, is most effective against the adult stage of the flea life cycle.

Contraindications

There are no known contraindications to Trefexis, though caution should be taken in breeding bitches so discuss this with your veterinarian. As per the instructions, don’t use in puppies younger than 8 weeks of age or in dogs with pre-existing heartworm infections.

Palatability

Trifexis is a flavored chewable tablet. Data shows that in a group of client-owned animals where 175 dogs were each offered Trifexis once a month for 6 months, their dogs voluntarily ate 54% of the doses when offered the product as a treat, and 33% of the doses when offered in or on food. The remaining 13% of doses had to be given like other tablet medications.

Pros
  • Requires a prescription, meaning your pet will be regularly examined by a veterinarian so any health problems will be picked up on more quickly
  • An adulticide flea product, reducing numbers of adult fleas quicker
  • A chewable tablet, which could mean it is more easily accepted by some dogs
Cons
  • 8 weeks of age is the youngest that a puppy can be treated with this product (and 5 lbs in body weight)
  • Caution in breeding bitches advised

divider 9

Overview of Sentinel

Sentinel for dogs (51-100 lbs)
Image Credit: Chewy

Ingredients

Sentinel contains milbemycin oxime and lufenuron. Each tablet is formulated to provide a minimum of 0.23 mg/pound (0.5 mg/kg) of milbemycin oxime and 4.55 mg/pound (10 mg/kg) body weight of lufenuron.

Indications

Milbemycin oxime is a macrocyclic anthelmintic with invertebrate neurotransmission. Sentinel is indicated for the prevention of heartworm disease (Dirofilaria immitis), for the prevention and control of flea populations, and the control of adult hookworm (Ancylostoma caninum), roundworm (Toxocara canis and Toxocara leonina), and whipworm (Trichuris vulpis).

According to Sentinel’s product information, dogs should be tested for the presence of heartworm before treatment with this product as an alternative product may be required to kill adult heartworm and microfilariae.

Instructions for use

Sentinel can be used in dogs and puppies aged 4 weeks or older and weighing 2 lbs or more.

Dosage

The tablets are given once a month by month and must be given with or shortly after food to ensure effective absorption of the active ingredients. Make sure the appropriate tablet size is used for your dog’s body weight and that the entire tablet is eaten.

The product can be given all year round at continuous monthly intervals to provide maximum protection.

Mechanism of action

The two ingredients in Sentinel serve different purposes.

Milbemycin oxime is a macrocyclic anthelmintic that interferes with invertebrate neurotransmission. This eliminates the tissue stage of heartworm larvae, and the adult stage of hookworm, roundworm, and whipworm infestations.

Lufenuron is an insect development inhibitor that breaks the flea life cycle by affecting the development of the flea eggs. It does not affect adult fleas. A flea bites the dog and ingests blood containing lufenuron, which is then deposited in her eggs. This stops the flea eggs from hatching into adults, helping to break their life cycle.

A concurrent adulticide product may be required to reduce the number of fleas more quickly, especially if there is a large flea infestation. Otherwise, it could take several weeks to see a noticeable drop in flea levels.

Contraindications

No real contraindications are noted, other than not to use in puppies under 4 weeks of age or in dogs that have pre-existing heartworm infections. The product appears to be safe at normal doses for pregnant and nursing bitches.

Palatability

The manufacturers of Sentinel claim the product is palatable, but no data was found to quantify this.

Pros
  • Requires a prescription, meaning your pet will be regularly examined by a veterinarian so any health problems will be picked up on more quickly
  • Can be used safely in very young puppies (4 weeks or older and weighing 2 lbs or more)
  • Safety data is provided regarding use in pregnant bitches
Cons
  • Breaks the flea life cycle by affecting egg development, meaning a separate adulticide product may be needed to reduce adult flea numbers more quickly
  • Not a chewable tablet, which may be an issue for some dogs

Divider 3

How Do the Two Products Compare?

Price range

Probably similar – both are prescription tablet medications given monthly so the cost will be in the same region. Both medications treat several parasites in one hit, so they may be more costly than some more narrow-spectrum parasite products on the market.

Instructions for use

Sentinel can be used in very young puppies aged 4 weeks and over, or 2 lbs body weight, whereas Trefexis can only be used in dogs 8 weeks and older and weighing at least 5 lbs.

pills
Image Credit: Pexels, Pixabay

Mechanism of action

Trefexis contains lufenuron, which is an insect development inhibitor preventing the development of flea eggs, whereas Sentinel is an adulticide that kills adult fleas.

Tablet type

Trifexis is a chewable flavored tablet whereas Sentinel is just a flavored tablet.

Palatability

Both products claim to be palatable, but only Trifexis provides data to back this up, with just over half of the doses in one study being taken plain like a treat.

Safety in breeding bitches

Trefexis advises caution when using in breeding bitches, so you will need to discuss this with your veterinarian. Sentinel appears to be safe for use in pregnant and nursing bitches at the recommended dose.

pet owner giving pill medication to dog
Image Credit: Jus_Ol, Shutterstock

Divider 2

What The Users Say

We have had a look at various pet-parent forums to see what the users of these products had to say about them. Our research showed mixed reviews of both tablets, mainly based on the palatability of the medications.

Some users say that “Trifexis smells like mold” and that their dog is reluctant to take the tablet for this reason. However, other users of Trifexis report how effective the product is and that it’s their product of choice for monthly parasite prevention.

Users of Sentinel say, “it is very easy to administer it to my pet and from present and past use has been very effective.” And “our dog is fussy so I expected him to reject these tabs but he loved it.”

However, other users claim their dog wouldn’t take the tablets!

What we take from this is that palatability may depend on the individual dog. Some will willingly take a tablet whereas others won’t! There is no clear-cut winner in this.

It is worth bearing in mind that dogs do smell things on a different level to us, so the product’s odor is no reflection of its efficacy and may not impact your pet’s willingness to take it. Both products have been licensed for use so their effectiveness against their target parasites has been scientifically proven.

Divider 5

Conclusion

Sentinel and Trifexis are broadly similar but there are a couple of differences between them. The main variation is that Trifexis is a flea adulticide, capable of killing adult fleas, which means more rapid results in the face of an outbreak. However, if you need to treat very young or small dogs then you might have to go for Sentinel for safety reasons.

Both tablets will need to be given at the correct dose for your pet’s weight once a month, to ensure maximum effectiveness. Missing doses may leave your pet open to parasite infestations, so don’t take the risk!

Further reading

Cat looking up>

join our newsletter today

And get our latest articles, food recall alerts, exclusive content, insider pricing, care guides, sale alerts & more for free!

Dog looking up>