Spinosad (Comfortis™) for Dogs and Cats


Overview of Spinosad (Comfortis™) for Canines and Felines

  •  Spinosad, Comfortis™, is a oral drug that provides flea control for one month. It contains antiparasitic agents used to kill and prevent fleas in dogs and cats.  Some combination products of spinosad mixed with milbemycin called Trifexis®
  • Comfortis™ is the first FDA approved chewable beef-flavored tablet for treatment and prevention of flea infestations. The active ingredient in Comfortis™ is spinosad. Spinosad is a member of the spinosyns class of insecticides.
  • Comfortis™ is a beef flavored oral tablet.
  • The effects last about 30 days against fleas. It is documented to begin killing fleas within 30 minutes.
  • Comfortis™ is a Prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • Brand Names and Other Names of Spinosad

  • This drug is Registered for use in dogsonly.
  • Human formulations: None
  • Veterinary formulations: Comfortis™ (Lilly)
  • Uses of Spinosad for Dogs and Cats

  • Comfortis™ is used in the control and treatment of adult flea infestations in puppies and dogs kittens and cats. For more information on flea infestations, please see Flea Infestation in Dogs and cats. 
  • Comfortis™ may benefit pets with Flea Allergy Dermatitis.
  • Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, Comfortis™ can cause side effects in some animals.
  • Comfortis™ should not be used in animals with known hypersensitivity or allergy to the drug.
  • Comfortis™ is approved for use in dogs and puppies over 14 weeks of age. It should be used with caution in breeding females and in dogs with epilepsy.
  • Comfortis™ may interact with other medications. Consult with your veterinarian to discuss using other medications when your pet is on Comfortis™. One interaction of note is when used with high doses of ivermectin – have resulted in signs of ivermectin toxicity in some dogs.
  • Comfortis™ is an oral agent. The most common side effect noted was vomiting. Other adverse reactions included decreased appetite, lethargy, redness of the skin, hyperactivity and excessive salivation.
  • How Spinosad is Supplied

  • Comfortis™ is available as an oral chewable tablet. It is dosed by body weight. Available sizes for dogs and cats include:

    5 – 10 pounds – 140 mg tablet
    10.1 – 20 pounds – 270 mg tablet
    20.1 to 40 pounds – 560 mg tablet
    40.1 to 60 pounds – 810 mg tablet
    60.1 to 120 pounds – 1620 mg tablet

    Dogs over 120 ponds should be given the appropriate combination of tablets.

  • Dosing Information of Spinosad for Dogs and Cats

  • Medication should never be administered without first consulting your veterinarian.
  • The dose of Comfortis™ for preventative flea control is administration of the product every 4 weeks throughout the flea season.  Comfortis is dosed by body weight in dogs and cats. The dog and cat products are the same, just dosed differently. 
  • Treatment can begin any time of year but should ideally begin 1 month prior to flea season.
  • Comfortis™ should be administered with food to maximize effectiveness.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. The manufacturer suggests monthly treatments to protect against flea re-infestation. Be certain to complete the prescription unless specifically directed by your veterinarian.
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    Anti-Parasitic Drugs (External)



    Anti-Parasitic Drugs (External)


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