Sentinel vs. Trifexis: Which All-in-One Preventive Is Best for Your Pet?

Which heartworm preventative is right for your dog?

If you’re like most pet owners, you want to provide your pet with the best protection from parasites with the least risk, hassle (for you and your pet), and cost. To help you decide which all-in-one preventive is best for you, we’ve put together a comparison of two major all-in-ones: Sentinel and Trifexis.

Similarities between Sentinel and Trifexis

Both Sentinel and Trifexis:

  • Contain the active ingredient Milbemycin Oxime, so they both treat and control roundworms, hookworms, and whipworms and protect against heartworms
  • Are chewable tablets that should be given once a month
  • Require a prescription from your veterinarian
  • Can be purchased online at 1-800-PetMeds

Differences between Sentinel and Trifexis

  • Cost
    One dose of Sentinel costs about $5 less than one dose of Trifexis.
  • Age at which each can be administered
    Sentinel can be given to puppies at beginning at 4 weeks; Trifexis can be given to puppies beginning at 8 weeks.
  • Minimum weight requirements
    Sentinel can be given to dogs as small as 2 pounds; Trifexis can be given to dogs as small as 5 pounds.
  • Flea control properties
    Sentinel contains Lufenuron, which prevents flea egg development and ends the flea life cycle, but doesn’t kill adult fleas; Trifexis contains Spinosad, which kills fleas (it has been proven to kill 100% of all biting fleas within four hours).
  • Cautions
    You should be cautious when giving any medication to your pet. And make sure you mention any other prescription medications or supplements you’ve given your pet to your veterinarian so he or she can check for drug interactions. Both have the potential for drug interactions. Trifexis carries the following caution: “Serious adverse reactions have been reported following concomitant extra-label use of ivermectin with spinosad alone, one of the components of Trifexis chewable tablets.”
  • Side effects
    With Sentinel, side effects are rare, but they can occur and may include vomiting; Trifexis may cause vomiting, and other side effects are less likely but possible.
  • Customer reviews
    Sentinel has a 4.4-star rating average from online shoppers and Trifexis has a 3.7-star rating average from customers.

We hope that this comparison has helped you decide which all-in-one preventive is right for you. Once you’ve decided, we hope you’ll visit 1-800-PetMeds for all of your pet supplies. Happy shopping!

Update 11/13/2013:  According to the FDA and Eli Lilly, Trifexis is safe and effective when used according to label instructions.  Unfortunately a small percentage of dogs may experience adverse reactions when taking this or any medication.  We encourage pet owners to consult their veterinarian before administering Trifexis or any other medication to their pets.

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  1. We’ve been using Trifexis for years with our Chocolate labs. No issues, but the large pills (for 75lb dogs) are apparently really bad tasting /smelling. Neither of our dogs will willingly take them and find them in everything!

  2. I have a Chihuahua and pit bull mix. he is maybe 2lb!!! my doctor told me to give a half a dose now and next month the other ? is what do other think and should I go ahead and give the half..
    Im just nerves to give it to him do to he is so small and young!! how ever I need to treat the stool worms!! please let me know your thoughts asap.. Im so turn on what to do!!

  3. I just experienced adverse reactions using Trifexis on my 4.3 pound yorkie. He became very lethargic and vomited twice and the poor thing had muscle twitches. It lasted a full 24 hours. Even his eyes were half masked and it seemed he could not focus. He is 1 yrs. old. I will NEVER use Trifexis again.

  4. My dog hates taking his trifexis, I tried to look into an alternative but doesn’t seem to be another one out there. He is a 2 year old terrier mix, 11lbs.

  5. I lso, cannot get my 8 yr. old Bichon to take it. I’ve tried, cheese, peanut butter, ice cream, but she can smell it no matter what. Actually, I can’t blame her, Trifexis smells so bad, I can hardly crush it up with out turning my head for a breath of fresh air. And, the pill is so large, I refuse to try to cram it down her throat. She, is 21 lbs, and on the 20.1 – 40 lb pill. Why can’t they (Elanco) at least try to coat the pill with a slick coating to help the pill go down in one gulp, and to mask the odor. These are pets, part of our family, they deserve a little consideration. They can do it for people, they SHOULD do it for our girls and boys. People understand when they are given a medication that is gross to help them stay well. Our kids just know that mom or dad is making them take something that they hate.
    $25.00 + for each tablet, they should be able (with out more R & D) to make a tablet ALL dogs can get down. But, then your kid may just keep it down each time. But, instead you get advice….if your dog throws it up, then give him or her a second tablet. Unless, I’m not able to add, now we are at $50.00 a dose.
    Seems to me, cool old money may be at the center of our problem. We keep buying, they don’t change a thing, our little ones are the ones that pay the real price. Elanco doesn’t care, why should they…they aren’t the ones who force this medication down our kids throats. If this was a human child we would not put up with this situation, when there is a simple change they could make.
    Yes, I keep on doing it to protect my little girl. But, it’s getting harder and harder to keep forcing my girl to take this. My little girl looks up at me every time now, wondering why I am doing this to her. And, I’m getting sick of it.

  6. Moved to SC in summer 2015 and our vet switched both miniature schnauzers to Trifexis from Sentinel. Said the worms, fleas, etc. were terrible here. Two months later one dog would have diarrhea within several days of taking Trifexis. The other one was fine. It took us a few months to figure out the cause and we stopped it, but not before the sick one developed irritable bowel syndrome. That was followed in 8 months with adenocarcinoma, which took him relatively quickly. I’m convinced that Trifexis started him down this path (his first 6.5 years were great) as he mirrored the 1% of dogs with severe reactions on the Trifexis warning sheet. I’ll never use Trifexis again! Have been on Revolution since then with our other dog and recently got a new puppy. Thinking about going back on Sentinel since they never had any problems and it’s a stronger preventative.

  7. We’ve been using Trifexis for several years on our our 100% Custom Blend Terrier who usually weighs around 52lbs, and You’re right about the smell. We have a custom blend 100% terrier who typically weighs 52 lbs~. It is a battle each month, we’ve tried all the tricks we can think of, though we are limited on what tricks we CAN use because she is prone to pancreatitis. Some months we wind up just having to shove it down her throat which afterwards inevitably makes me feel guilty. I so wish the manufacturers would do something to coat these nasty smelling pills and make them more palatable. In truth, however, what disturbs me more than anything is the fact that I am basically giving my pet what amounts to an oral pesticide. All the pesticides I know of are poisonous. Why give one to my dog? Couldn’t this potentially cause problems somewhere down the line, or in some cases immediately? Why can we not develop something less harsh, more “organic” if you will, more natural but still effective. I can guarantee the solution is out there, we’re just not looking in the right place, or looking for it at all!

  8. I would really love to give my dog something other than Trifexis, but Sentinel not killing adult fleas bothers me. I’m still doing research but it seems many people use a combination of both oral and topical meds? I just have to find the best combo for my dog because she HATES Trifexis and it’s a struggle administering it monthly.

  9. I have had apprehension about using Trifexis for my Shih-Tzu, however he has been on it for over 2 years with no apparent issues. He will NOT eat them no mater how I try, I’ve used Pill Treats and they make him throw up every time, if I break it up into his food he will pick out the pieces no mater how small I make them, or not eat it at all. I am now just putting them down his throat, which he doesn’t seem to fuss over.

    I have not tried Sentinel as it does not kill fleas which are rampant in my area, and I really don’t want to have to give him even more medications. I do use topical flea treatments after every bath, and if I see any (living) fleas on him.

    I had tried HeartGuard but haven’t heard great things about it, and it is very limited to only heartworm protection.

    It is a shame that they charge so much for Trifexis, and Elanco is a crook and on on several occasions wouldn’t honor the rebates I’ve sent in. So buyer beware…

  10. I agree with Char and Rob, regarding the horrid smell/taste of Trifexis. I have 4 dogs between 4 lbs and 9 lbs, ages between 5 and 7 yrs. The two smallest (4 and <5 lbs) get 1/2 dose monthly. I have been putting it in soft cheese and/or peanut butter and giving it before breakfast when they are the most hungry. Annie, my 5-lb toy poodle, can smell heavily disguised Trifexis before she even gets close to it and turns to run away. I've tried giving her 1/4 dose (twice) and sometimes can get her to take one of those. I have even taken her to the vet to have two techs try to get a half-dose into her in pill pockets and finally using a straw-like gadget that you blow into to get the pill down. That took half an hour. I have written to Elanco about their stinky product a couple of times and received no reply. I'm going to ask my vet about using Sentinel instead of Trifexis, at least for little Annie.

  11. I’ve been giving my dog Trifexis for years. I’ve never had a single issue with negative side effects, etc and the medications have prevented all that they have claimed to. Previously, he had been on Heartgard. I switched him over for the added coverages. I’m truly very sorry for the loss of your dog- but as stated by a previous commenter, you really shouldn’t make such claims and not specify the medication given. As you can see, it causes a great deal of concern and confusion amongst other posters and can hurt a business unfairly.

  12. I’ve been giving my mini poodle trifexis for 2 years now he weighs 15 lbs. The worst side effect on him is scratching, it drives me crazy. I need to get him off of trifexis and put him on something else.

    Any suggestions on what I could put him on that doesn’t make him scratch. I’ve bought so many things to put on him to quit his scratching to no avail.

    Thank you.

  13. I have a long haired Doxie and the vet put her on trifexis and for five years she had seizures every couple of months, I decided to change her to Sentinel, and she has not had anymore seizures since.

  14. Our current vet does not carry trifexis and after 2 years on Sentinel, it seems the last week before her next dosage the fleas are back in a vengeance. Back when she took Trifexis(3-4+ years on it), there was never a flea issue at all, though as others point out, it is a fight to get her to take the pill (usually ends in having to force it down). I’m thinking of trying to convince my vet to either start carrying it, or give us the prescription to buy from somewhere else as I no longer feel Sentinel is effective on fleas.

  15. Smash the Trifexis between two spoons and mix in with some wet food.

  16. My dog, sheba, was minus fleas or worms when she was on Trifexis. But, I can’t afford it right now. So, I am looking for a cheaper option.

  17. Hi Misty. At this time, there is no generic equivalent for Trifexis. However, instead of an all-in-one product you could look into a separate flea treatment and heartworm preventative, for which there are less expensive alternatives. We recommend consulting with your vet to determine the best choice for Sheba.
    ~ Abby, PetMeds Pro

  18. My 8 lb yorkie has been on trifexis for 3 years she’s now 4. She hates to take it. I had to put it down her throat. Well we had problems and they had to go labs on her and her liver enzymes were 700 which are extremely high. That was done 5 days after me giving her trifexis. After reading the material it can cause liver damage. How many dogs get labs to know this? I did notice some yucky stools occasionally but I shrugged it off as it would get back to normal. But after talking to my vet no more for her!! Have your dogs enzymes checked!! I’m gonna try sentinel.

  19. My dogs one a dingo and one a boogie , have taken trifexis since I have them which was 5 months old. They are now 9 years old , and still taking trifexis . Numerous times I thought about switching, but, my dingo takes it 30 mins right after a meal with cream cheese and he , thank God never gave me a problem. My boogle , she is 22 pounds. She 30 minutes after she eats she will sometimes take it with salami, cream cheese, American cheese, ham just depends on her mood. They do not get that tired anymore since they have been on it so long , but sometimes my little one will throw up just once foamy white and never again for months. Don’t know why !
    As they get older I will ask the doctor to change them to something else .

  20. I have a Shih-Tzu, she was put on Trifexis at early age and besides an occasional throw up that we just thought was her gagging on hair or something everything was fine at first. We took our dog to get spaded about 2 years ago and the blood work done before surgery showed high liver enzymes. Thru months of testing and seeing specialist we ended up switching vets because we kept being referred to specials to do what other Animal Hospitals are capable of doing. We continued to test the enzyme level and it kept increasing to about 280. Well her trifexis medication ran out in December during the transition to another vet that we had to use to get an ultrasound because the “hospital” we were going to didn’t have the equipment. After consulting with the new Vet they recommend a liver biopsy so we waited to put aside the money for the procedure and during this time no trifexis was given to my dog from December to the end of February when we returned to the vet to schedule the procedure. Because of the amount of time between visits they needed to check the liver function again to make sure she was OK for anesthesia. The vet called back today and said she doesn’t recommend a liver biopsy at this time because the enzyme level has now dropped to 118. When i questioned whether thrifexis could cause this the vet pulled up a web site and they didn’t see any information regarding trifexis and liver enzymes increase.

  21. I have the cutest little Yorkie. He is getting up in age but has been in very good health. I have never brushed his teeth as He doesn’t even like me to brush him, he is so layed back and calm. My groomer really likes to work on him.

  22. All my dogs have extreme flea allergies. Trifexas is the only thing that has helped them. They hate the pills and i understand why, they are huge and if they taste as bad as they smell, yuck. I grind them up and mix it with peanut butter. They lick the bowl clean no problem and they have not lost any hair sence.

  23. We have 1 1/2 yr. old shepherd she is the light of our lives as is our 13yr. Old Puggle. I took us the three doses on each of them before we realized that the Trifexis hype/paranoia is real!!!vomiting, diarrhoea, snapping at the air, malaise and numerous other side effects lasted almost a week on the final dose our dogs will ever receive – just goes to show big pharmaceutical in the human or animal world has no soul, morals or scruples. The almighty dollar rules the difference being- animals are at your complete mercy!!!!!
    Shameful at best!

  24. Fyi. I know how bad trifexus smells so I put a slit across 1/2 the opening and let it air out over night. Then wrap in a small piece of cheese. Airing out seems to help lighten the smell. I have 3 dogs all around 12 lbs. Hope this helps

  25. My girl is a lab English spaniel mix that weighs approximately 60 lbs. She’ll be 5 in June and has taken trifexis most of her life but has gotten to the point where nothing works. I’ve tried peanut butter, airing out the tabs, covering in cheese or grinding up the tab and mixing with bacon grease or wet food. She would literally go days without eating before taking the medication. If I force it down her she throws it up so I’m at the point of giving up and going with something else. Problem is if I can get it down her it works really well.

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