Comfortis Chewable Tablet for Dogs, 20.1-40 lbs, (Green Box), slide 1 of 1

Comfortis Chewable Tablets for Dogs 20.1-40 lbs & Cats 12.1 -24.1 lbs, 6 treatments (Green Box)

Prescription Item

  • Price:

    $105.99 FREE Shipping on this item

Autoship: &Save

$100.69(Save an extra 5%)

Simply select Autoship at checkout for easy regular deliveries.

In stock

This item requires prescription approval. Details

Medications ship separately. Delivery times may vary. Details

We'll collect your pet's prescription information at Checkout.

cw-icon-heart Created with Sketch. Add to Favorites

Comfortis is a chewable medication prescribed by veterinarians for dogs and cats to help treat -- and possibly even prevent -- flea infestations for up to one month. These flavored tablets can be added to your pet's favorite food and only need to be given to your canine companion once a month to help combat fleas.


Comfortis kills fleas and is indicated for the prevention and treatment of flea infestations, for one month, on cats and kittens 14 weeks of age and older and 4.1 pounds of body weight or greater.

Possible Side Effects

The most common side effect reported in dogs is vomiting.

Drug & Food Interactions

There are no known drug interactions while using Comfortis.


Comfortis chewable tablets are for use in dogs and puppies 14 weeks of age and older. Use with caution in breeding females. Use with caution in dogs with pre-existing epilepsy. The safe use of Comfortis chewable tablets in breeding males has not been evaluated.

Dosage Chart

Color on BoxWeight RangeStrengthDosageProduct Page
PinkDogs 5-10 lbs / Cats 4.1-6 lbs140 mg SpinosadGive orally once a month✓-Click Here
OrangeDogs 10.1-20 lbs / Cats 6.1-12 lbs270 mg SpinosadGive orally once a month✓-Click Here
GreenDogs 20.1-40 lbs / Cats 12.1-24 lbs560 mg SpinosadGive orally once a month✓-Click Here
BlueDogs 40.1-60 lbs810 mg SpinosadGive orally once a month✓-Click Here
BrownDogs 60.1-120 lbs1620 mg SpinosadGive orally once a month✓-Click Here
  1. Prescribing Information

See all items by Comfortis

  • Item Number
  • Generic Name
  • Common Brand Name(s)
    Comfortis, Trifexis
  • For Use With
    Dogs & Cats
  • Administration Form
  • Brand
  • Lifestage
    Adult, Senior, Puppy
  • Breed Size
    Small Breeds, Medium Breeds
  • Product Form
    Chewable Tablet
  • Strength
    560 mg Spinosad
  • Health Condition
  • Drug Type

560 mg Spinosad.

Recommended Dosage

Dose varies based on pet's weight. Use according to your veterinarian's instructions. Comfortis is generally given once a month, but you should always follow your veterinarian's directions. It is recommended to give Comfortis chewable tablets with food.

Storage Instructions

Store at temperatures between 68° - 77°F.


What are Comfortis Tablets?

They’re beef-flavored, chewable tablets you give to your dog or cat to kill fleas and prevent flea infestations for one month. Comfortis chewable tablets are recommended for monthly use in cats 14 weeks of age or older and 4.1 lbs of body weight or greater and in dogs 14 weeks of age or older and 5 lbs of body weight or greater.

What is Spinosad?

Spinosad is the active ingredient in Comfortis. It belongs to a class of antiparasitics known as spinosyns, which are derived from a naturally-occurring soil microbe. It works by attacking the nervous system of insects, causing the rapid death of adult fleas.

When should treatment with Comfortis begin?

Treatment can begin at any time of the year. Comfortis is most effective when given one month before fleas become active, with continued monthly dosing through the end of the flea season. In areas where fleas are common year-round, monthly treatment with Comfortis chewable tablets should continue through the entire year without interruption. To minimize the likelihood of flea re-infestation, simultaneously treat all animals in your household with an approved flea protection product. Consult your veterinarian for the flea treatment options most appropriate for your area. See also, what should I discuss with my veterinarian regarding Comfortis for my dog or cat?

How quickly will Comfortis (Spinosad) kill fleas?

Spinosad, the active ingredient in Comfortis, began killing fleas in 30 minutes and killed 100% of fleas on dogs and 98% of fleas on cats in just four hours in controlled laboratory studies. Comfortis chewable tablets kill fleas before they can lay eggs.

How long does Comfortis last?

Comfortis has demonstrated full effectiveness for an entire month.

Does seeing fleas on my dog or cat means the treatment isn't working?

Comfortis kills fleas before they can lay eggs when used monthly, according to the label directions. If you see fleas on your dog or cat within a month after your pet receives Comfortis, they are most likely new fleas. Because your pet has been treated with Comfortis, these new fleas will be killed before they can produce eggs that contaminate your home. Continued monthly use of Comfortis can prevent any new flea infestations.

Your pet can experience continued exposure to fleas living in the environment. It’s important to treat all animals in the household with an approved flea product to help control the flea population. Learn more about controlling flea infestations in your home.

Is it safe to give Comfortis (Spinosad) to my dog or cat?

Comfortis has demonstrated to be safe in healthy dogs and cats when used according to label directions. Use only for cats and kittens 14 weeks of age or older and 4.1 lbs of body weight or greater, and for dogs and puppies 14 weeks of age and older and 5.0 lbs of body weight or greater. The safe use of Comfortis in breeding, pregnant or lactating cats and dogs has not been evaluated.

My pet has allergies, can he still take Comfortis?

Comfortis contains beef flavoring made from a pork-based protein. If your pet has an allergy to pork, you may need to consider an alternative for flea treatment and prevention. Please discuss these options with your pet's veterinarian. The use of ivermectin at higher than FDA-approved doses at the same time as Comfortis can result in serious side effects.

What side effects might occur with Comfortis?

As with any medication, sometimes side effects occur. See the Comfortis label for complete safety information.

For cats: In some cases, cats vomited after receiving Comfortis. If vomiting occurs within one hour of administration, re-dose with another full dose. Additional adverse reactions observed in studies were lethargy, decreased appetite, weight loss, and diarrhea. Use with caution with concomitant extra-label use of ivermectin. See the Comfortis label for complete safety information.

For dogs: The most common adverse reaction reported is vomiting. Other adverse reactions reported in decreasing order of frequency are depression/lethargy, decreased appetite, incoordination, diarrhea, itching, trembling, excessive salivation and seizures. Following concomitant extra-label use of ivermectin with Comfortis, some dogs have experienced the following clinical signs: trembling/twitching, salivation/drooling, seizures, ataxia, mydriasis, blindness, and disorientation. See the Comfortis label for complete safety information.

How should I give Comfortis (Spinosad) to my pet?

Administer Comfortis with food for maximum effectiveness. Because Comfortis is a flavored tablet, it can be offered just prior to or just after feeding. You can also administer Comfortis as you would other tablet medications. Visit the Dosing & Administration page for more details, or download the Comfortis label. Each box includes reminder stickers for your calendar to help remind you to administer each dose. You can also sign up for monthly text or email reminders.

How much food do I have to give my pet when adminisering the Comfortis Tablet?

In field trials, dog and cat owners were instructed to give the Comfortis tablet with food. However, the quantity of food was not specified and Comfortis was still effective. An option is to give Comfortis immediately before a regularly scheduled meal. For free feeders (dogs or cats who nibble throughout the day), you might take food away at night, administer Comfortis first thing in the morning, then put the food back down.

What id I miss a dose of Comfortis?

Give your pet his or her regular dose immediately, then resume a regular monthly schedule. To help you remember to dose your pet, sign up for monthly email or text message reminders. For complete safety information, view the Comfortis label.

What if I give more than the prescribed amount of Comfortis to my pet?

Contact your veterinarian if you believe your pet has ingested more than the recommended dose of Comfortis. Visit the Dosing & Administration page for more details, or see the Comfortis label for complete safety information.

Should I restrict my pet's activity or contact with my pet after the tablet is consumed?

No. You can continue normal activities and interactions with your pet.

Can other medications be given while my pet is taking Comfortis?

Comfortis is not contraindicated for use with any veterinary drug/product when they are administered at labeled doses. However, while labeled heartworm preventatives are not an issue, you should not use Comfortis concurrently with extra-label doses of ivermectin in dogs and should use caution in cats. Make sure your veterinarian is aware of all products that you intend to administer to your pet. In well-controlled field studies, Comfortis chewable tablets were administered safely in conjunction with other frequently used labeled products, such as vaccines, anthelmintics, antiparasitics, antibiotics, steroids, tick control products, anesthetics, NSAIDs, antihistamines, alternative/herbal remedies, shampoos, prescription diets, and most generally prescribed medications.

What should I discuss with my veterinarian regarding Comfortis for my dog or cat?

Your veterinarian is your pet's healthcare expert and can make the best medication recommendations. This includes the prevention, control and/or treatment of parasites such as fleas, heartworms and intestinal parasites. These parasites can cause conditions including flea allergy dermatitis, anemia, and heart disease. Key points of your discussion might include:

  • The best time to start flea treatment in your geographic region.
  • What administration method will work best for your pet.
  • What to do if you miss a dose of Comfortis.
  • What other medications you give your pet.
  • What to do about a severe flea infestation.
  • What steps you can take to prevent a flea re-infestation in your home.
Rating: 4.1 of 5 stars 49 Reviews 49 Reviews 4.1 out of 5 Stars

84% Recommend

84% of reviewersrecommend this product

Rating: 4.1 of 5 stars 4.1 / 5

You've Already Reviewed This Item

49 Reviews

Showing 1-10 of 49 Reviews

  • 5 out of 5 stars

    Best I've found yet

    By KaspersDad on Dec 2, 2020

    I was advised by my Vet to try Comfortis for flea and tick control. We had been using a topical for flea & tick control but my dog always acted a little off after treatment and honestly the fleas didn't seem to mind much. In the last month that we started using Comfortis the control was nearly immediate. I have a Kooikerhondje and he has a bit of a sensitive stomach and we saw no adverse effects from the treatment and as I understand it we can expect no reduction in efficacy as long as we stick to a monthly schedule unlike topical treatments diminishing effects.

    You liked it! Something went wrong. Please try again later. Report
  • 1 out of 5 stars

    Do not mix with food

    By Nope on Jan 14, 2021

    Not ideal for cats. I accidently ordered the chewable. I wasted them by trying to get my cats to take it lol. What a mess. I should have mixed with water and gave with a syringe.

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Great product

    By Suzanne on Sep 28, 2020

    I would recommend this medicine for cats and dog.. we usually have a fleas up until October or November but our dogs and cats have been on this medicine for about a year and this year we have NOT had any fleas.. it works wonders, my cats do not like it but we do get them to take it and they have not had any fleas either. It has been great this past summer not having fleas on our animals or in our house...

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Chewy fir life

    By Shannon on Nov 15, 2020

    Comfortis and or Trifexis are the only way to go.might be spendy but it’s worth it. No harsh chemicals and takes care of everything.

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Terrific product!

    By Mjwhebellee on Dec 30, 2020

    Product is better than fleas protection from my cats and us the owners. Resolution after ingestion is very fast acting.

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    It wonderful n works

    By Sable on Jul 31, 2020

    My cat is a Maine coon n can't put tropical anything on his back. He doesn't like the smell or the pill is big my vet can get it down his throat cuz he is scared don't want to stay for strivite crystal or diabetes type 1 insulin. I just mess with him n catch him off guard n get it down his throat n no reactions from it n I give him treats after. My hubby pill cuts it in 4 n puts it in his mouth don't like it but it works every month. No fleas.

    You liked it! Something went wrong. Please try again later. Report
  • 3 out of 5 stars

    HUGE fight to get in pets

    By chrisc on Jul 6, 2020

    None of my 6 pets would eat the comfortis, even in pill pockets. huge fight to get them in my pets, even when broken into small pieces (pills are too big for cats/small dogs). my dog would swallow the pill pocket and spit up the pill. it smelled very medicinal. 3 of them vomited within a half hour of taking the comfortis. i still found fleas on my cats, tho much fewer. frustrating, coz frontline no longer works at all

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    No fleas for Buddy!

    By Buddy on Jun 10, 2020

    I've been hesitant to try oral flea meds because I have heard the horror stories about permanent seizures. After researching and advice of a friend I decided to try Comfortis after a horrible flea season! It worked great! Fleas were gone in hours! Buddy didn't like the taste but put in a pill pocket and he took it. Most importantly, there were no seizures!

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Easy for my cat to eat

    By Rachael on Aug 6, 2020

    I crush it up in his food and he eats it. Seems to work fine since we’ve never had a flea issue. My cat is allergic to topical meds, so this is a great option.

    You liked it! Something went wrong. Please try again later. Report
  • 5 out of 5 stars

    Best flea medication!

    By Yoko on Sep 16, 2020

    I have two small dogs and this medication works great. I haven’t seen a flea since they started this medication a year ago.

    You liked it! Something went wrong. Please try again later. Report