Comfortis Flea Preventative
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At a Glance
First FDA-approved monthly chewable flea preventative.
#1 veterinarian-recommended prescription flea-only medicine
Its active ingredient spinosad works to paralyze and eventually kill fleas.
Starts killing fleas after 30 minutes once administered.

How To Order Prescriptions Online

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Customer Reviews

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Rated 5 out of 5 by 258 reviewers.

  • Works well for dogs, hit or miss with cats
    Comfortis is awesome and works better than anything we've ever tried.... for the dogs. Our dogs take to it fine without any side effects. The only problem with them is they don't like eating it. Our little dog only takes it if we mush it into a ball of squishy American cheese because she absolutely will not eat it alone (and she eats anything!... else) Our big dog will only eat it when shoved into the center of a hotdog. But the biggest problem we have is with our cats throwing it up. Our old vet said to give it to them on an empty stomach... DON'T. My cats puke it up every time. Our new vet said to make sure they've eaten first. But to make sure they eat when we need them to, and not too much, we have to take their food away all day. Another problem we have is they won't eat anything but their regular food. They won't eat treats or anything we try to hand feed them so we have to force feed the pill to them. Then we definitely have to make sure to watch them for the first hour, like the instructions say, to make sure they keep it down because if they puke before the hour, it says it won't get into their system enough to work all month. Taking it after eating helps them but they still puke about 50% of the time. It's just too stressful for the cats especially if it's all for nothing because they ended up throwing it up. So unfortunately we have to stick with topical for them, which doesn't work half as good, but at least they don't go outside like the dogs. by on 04/30/2020
  • It works if the dog will eat it.
    I need to buy something else because my dog hates it. Today I cut up the pill (50+ lb size) into 8 pieces and hid the pieces in roasted hot dog bits and he still hesitated- and given that I can still smell the pesticide smell on my fingers from cutting it up, I don’t blame him. The pill is too large to shove it down his throat whole - about the size of two nickels stacked. If you have a greedy fast eater with weak taste buds, I’m sure it’s great, but it’s a stressful ordeal for me that I’d like to avoid in the future. by on 06/02/2019
  • Comfortis
    Seems to do the job. My dog hates the taste so I have to push it down her throat and give her a treat immediately after but that works. by on 02/21/2019
  • worng size tabet
    We ordered the pill indicated for the cats size. The pill that arrived is much larger than the ones we purchased from the vet. It is monthly torture to get her to take it. It did arrive fast. by on 01/30/2019
  • Works when nothing else will
    My poor cat has been through the ringer when it comes to fleas. He's allergic to flea bites, and we found he is allergic to most topical flea medications. We've tried everything from topicals, powders, flea collars, flea baths, and oral tablets. When we found Comfortis, it was a total lifesaver. We never find fleas on him anymore, and although he hates to take pills it is still effective when we crush it up and put it in his food so it's fairly easy to get him to take it. If you've tried everything and nothing will work, I suggest giving this a go! by on 12/04/2018
  • Works Great.
    My cat is a finicky eater and won't chew the tablet. I simply break it in half and pill her. Cleared up existing fleas and haven't seen one since. My other cat throws it up so had to switch to Bravecto for her. by on 08/24/2018
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