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Trifexis Vs Sentinel Flavor Tabs: Effectiveness and Safety for Dogs

Trifexis Vs Sentinel Flavor Tabs

See Which Flea Pill is Best for Your Dog


With so many options for flea control on the market, it’s tough to decide which one to go with.

Chewable tablets are easy, you only need to use them once per month, and there’s no messy residue or poison-coated collar to deal with. But what’s the difference between them?

Excellent question and one that many of our readers have had. By the end of this article, you’re going to know the differences between Trifexis and Sentinel Flavor tabs so that you can decide for yourself if either one is right for your dog.

What Do They Do?

Both Trifexis and Sentinel claim to kill fleas and protect against heartworms and intestinal worms so let’s take a look at the ingredients and see exactly how each chewable flea pill works.

Both Trifexis and Sentinel work for up to 30 days without repeat treatments being necessary.

Both pills contain milbemycin oxime, an anti-parasitic that kills hookworms, roundworms and pinworms. It also prevents heartworms by killing the juvenile worm while it’s still in the bloodstream. Finally, milbmycin oxime may be at least moderately successful at killing flea eggs though it has no effect on hatched fleas.

OK, so we have the heartworms and intestinal worms covered as both pills claim. What about fleas, though?

Trifexis also contains Spinosad, a neurotoxin that causes paralysis and death in adult fleas. It doesn’t have any effect on eggs or larvae though.

In addition to milbemycin oxime, Sentinel also contains lufenuron, a pesticide that is passed from the female flea to the egg, then prevents the larvae from developing an exoskeleton, thus killing it before it turns into a flea that can bite or reproduce. It has no effect on adult fleas, though.

Side Effects and Warnings

Side effects for both medications are basically the same though the spinosad in the Trifexis may have a slightly higher risk of vomiting. The best way to avoid this is to administer the flea tab with food. Also, Trifexis isn’t recommended for dogs with a history of seizures.

Other side effects include lethargy, drowsiness, depression, nausea, skin irritation, drooling, diarrhea and loss of appetite.


Both Sentinel and Trifexis are available only from your vet, so talk to him or her about what pill may be best for you. The primary difference between the two is that Trifexis is going to kill adult fleas right now but won’t do anything about eggs or larvae that are present, though it works on the adults as the fleas hatch and the larvae mature.

On the other hand, Sentinel doesn’t kill adult fleas but does eradicate the eggs so that your infestation will end as soon as a couple of lifecycles of fleas pass.

Both pills share the same side effects, so that really isn’t a determining factor.

If you’ve tried either of these or both of them, please share your experience with us in the comments section below!

2 Responses to “Trifexis Vs Sentinel Flavor Tabs”
  1. S Onorato says:

    Yes, I have used the Trifexis for about 2 years now with my Maltese.It works excellent! I have never seen a flea on my dog and all the heart-worm tests come back negative. She has no had any of the side effects to my knowledge. I was thinking of buying the sentinel to possibly save some money ( the Trifexis is very expensive) But now after reading about it, I prefer to stick with the Trifexis. The fact that it kills the adult flea is better.
    Luckily my vet matching prices with other vet, as long as they are in the US. And Trifexis usually gives you back $10 on 6 mos/ $20 on 1yr. So all that make it more affordable and it works! So I’m sticking with Trifexis.
    Thanks for the info.

  2. CK says:

    Have used sentinel in dogs before, rarely ever a flea. Trifexis, because shelter had used it when we got them, is no help at all for fleas. Changing them over to sentinel, that our last dog took up thru age 20.

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