Comfortis Chewable Tablets (Spinosad)

Only Available By Prescription

Top brand choice

What is a Generic Drug?

A generic drug is a copy of the brand-name drug with the same dosage, safety, strength, quality, consumption method, performance, and intended use. Before generics become available on the market, the generic company must prove it has the same active ingredients as the brand-name drug and works in the same way and in the same amount of time in the body.

The only differences between generics and their brand-name counterparts is that generics are less expensive and may look slightly different (eg. different shape or color), as trademarks laws prevent a generic from looking exactly like the brand-name drug.

Generics are less expensive because generic manufacturers don't have to invest large sums of money to develop a drug. When the brand-name patent expires, generic companies can manufacture a copy of the brand-name and sell it at a substantial discount.


Comfortis is a chewable tablet medication that eliminates fleas for dogs and cats. It is the number one prescription flea-only medication in America. It is also reported to kill 100% of fleas on dogs and 98% of fleas on cats within 4 hours of being ingested. It can be used on either dogs or cats that are 14 weeks of age or older, and weigh more than 4.1 lbs (cats) or 5 lbs (dogs).

The active ingredient in Comforts is Spinosad.


Comfortis should be administered once a month and based on the following guideline:


  • Weight: 5 - 10 lbs / Weight (in kg) indicated on pack: 2.3 - 4.5kg / Spinosad (140mg)
  • Weight: 10.1 - 20 lbs / Weight (in kg) indicated on pack: 3.9 - 6kg / Spinosad (270mg) (UK)
  • Weight: 20.1 - 40 lbs / Weight (in kg) indicated on pack: 9.1 - 18kg / Spinosad (560mg)
  • Weight: 40.1 - 60 lbs / Weight (in kg) indicated on pack: 18.1 - 27kg / Spinosad (810mg)
  • Weight: 60.1 - 120 lbs / Weight (in kg) indicated on pack: 23.2 - 36kg / Spinosad (1620mg) (UK)

Recommended U.S. minimum dosage for dogs is 13.5mg / lb per month 


  • Weight: 4.1 - 6 lbs / Weight (in kg) indicated on pack: 2.3 - 4.5kg / Spinosad (140mg)
  • Weight: 6.1 - 12 lbs / Weight (in kg) indicated on pack: 3.9 - 6kg / Spinosad (270mg) (UK)
  • Weight: 12.1 - 24 lbs / Weight (in kg) indicated on pack: 9.1 - 18kg / Spinosad (560mg)

 Recommended U.S. minimum dosage for cats is 22.5mg / lb per month. 

NOTE: For dosages above marked at the end with (UK) - UK doses Comfortis at a higher level than America. The weight in kg indicated on the UK sourced packs will be less than the actual weight when converted to lbs. Choose the appropriate pack size by your pet's weight in LBS. and the correct recommended U.S. minimum dosage (see above) of Spinosad will be shipped. 

Upon receipt, verify dosage (mg) indicated on pack matches the recommended U.S. dosage (mg) for your pet's weight in lbs. 

  • Comfortis chewable tablets should be given with food for maximum effectiveness
  • They are readily consumed when offered by hand prior to feeding
  • May also be given in food or by placing the tablet at the back of the tongue and encouraging the animal to swallow
  • Treatment with Comfortis chewable tablets may begin at any time of the year, but should preferably begin one month before fleas become active and continue until the end of the flea season
  • In areas where fleas are common year-round, continue treatment with Comfortis throughout the year
  • In order to minimize the likelihood of flea re-infestation, all animals within a household should be treated with an approved flea protection product 

As an alternate to year-round dosing, this medication can be given during the mosquito season and then for one month after the season ends.




  • Comfortis should be used with caution in breeding females, and dogs with pre-existing epilepsy
  • Vomiting has been seen on rare occasions
  • If vomiting occurs within an hour of administration, it is recommended that the animal is re-dosed with another full dose of the medication
  • Not for human use. Keep this and all drugs out of the reach of children

Side Effects

On rare occasions, a reduced appetite, lethargy, diarrhea, a cough, increased thirst, reddened skin, salivation, hyperactivity, an increased appetite, and vocalization have been seen in treated animals. However, this is most commonly the result of overdosing on the medication.

This information is for informational purposes only. It is not to be a substitute for the diagnosis, treatment, or professional advice of a veterinarian. Always seek the advice of your veterinarian or other qualified professionals with any questions you may have regarding a medical condition or the use of a particular medication.

IMPORTANT NOTE: The above information is intended to increase awareness of health information and does not suggest treatment or diagnosis. This information is not a substitute for individual medical attention and should not be construed to indicate that use of the drug is safe, appropriate, or effective for your pet. See your veterinarian for medical advice and treatment for your pet if you have any concerns.