Spinosad

Indications

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

Dosage and Administration

COMFORTIS is given orally once a month, at the minimum dosage of 22.5 mg/lb (50 mg/kg). Do not use the dosing schedule below when administering COMFORTIS to dogs, as it can result in an overdosage. Dosage Schedule for Cats: *Cats over 24 lbs should be administered the appropriate combination of tablets. Body Weight of Cat Spinosad Per Tablet (mg) Tablets Administered 4.1 to 6 lbs 140 One 6.1 to 12 lbs 270 One 12.1 to 24* lbs 560 One Administer COMFORTIS with food for maximum effectiveness. COMFORTIS is a chewable tablet that can be consumed by cats when offered by the owner just prior to or after feeding. Alternatively, COMFORTIS may be offered in food or administered like other tablet medications. COMFORTIS should be administered at monthly intervals. If vomiting occurs within an hour of administration, redose with another full dose. If a dose is missed, administer COMFORTIS with food and resume a monthly dosing schedule. Treatment with COMFORTIS may begin at any time of the year, preferably starting one month before fleas become active and continuing monthly through the end of flea season. In areas where fleas are common year-round, monthly treatment with COMFORTIS should continue the entire year without interruption. To minimize the likelihood of flea reinfestations, it is important to treat all animals within a household with an approved flea protection product.

Contraindications

There are no known contraindications for the use of COMFORTIS.

Warnings

Not for human use. Keep this and all drugs out of the reach of children. Keep COMFORTIS in a secure location out of reach of dogs, cats, and other animals to prevent accidental ingestion or overdose.

Precautions

Use with caution with concomitant extra-label use of ivermectin ( see

Adverse Reactions

and Post-Approval Experience ) . The safe use of COMFORTIS in breeding, pregnant, or lactating cats has not been evaluated. Adverse Reactions: In a well-controlled US field study, which included a total of 211 cats (139 treated with COMFORTIS and 72 treated with an active topical control once a month for 3 treatments), no serious adverse reactions were attributed to the administration of COMFORTIS. Over the 90-day study period, all observations of potential adverse reactions were recorded. Reactions that occurred at an incidence > 1% within any of the 3 months of observations are presented in the following table. The most frequently reported adverse reaction in cats was vomiting. Percentage of Cats (%) with Adverse Reactions Month 1 Month 2 Month 3 COMFORTIS (n=139) Active Topical Control (n=72) COMFORTIS (n=135) Active Topical Control (n=69) COMFORTIS (n=132) Active Topical Control (n=67) Vomiting 14.4 1.4 14.8 1.4 13.6 4.5 Lethargy 3.6 0.0 0.7 0.0 1.5 1.5 Anorexia 2.2 0.0 0.7 0.0 2.3 1.5 Weight Loss 1.4 0.0 0.0 0.0 3.0 0.0 Diarrhea 1.4 1.4 0.7 2.9 2.3 1.5 Over the 3-month (3-dose) study, vomiting occurred on the day of or the day after at least one dose in 28.1% (39/139) of the cats treated with COMFORTIS and in 2.8% (2/72) of the cats treated with the active topical control. Three of the 139 cats treated with COMFORTIS vomited on the day of or the day after all three doses. Two cats that received extra-label topical otic ivermectin on Day -1 of the field study developed lethargy on Day 1 after COMFORTIS administration on Day 0. Post-Approval Experience (2023) The following adverse events are based on post-approval adverse drug experience reporting for COMFORTIS. Not all adverse events are reported to FDA/CVM. It is not always possible to reliably estimate the adverse event frequency or establish a causal relationship to product exposure using these data. The following adverse events reported for cats are listed in decreasing order of reporting frequency: Vomiting, depression/lethargy, anorexia, behavioral changes, pruritus, diarrhea, ataxia, hyperactivity, hypersalivation, panting, vocalization, dyspnea, twitching, and seizures . In some cases, death has been reported. Some of these reports involved cats with cardiac disease, including cats with previously undiagnosed cardiac disease. Following concomitant extra-label use of ivermectin with COMFORTIS, some cats have experienced the following clinical signs: ataxia, trembling/twitching, seizures, mydriasis, disorientation, and transient blindness . Post-approval experience continues to support the safety of COMFORTIS when used concurrently with heartworm preventatives according to label directions.

Description

COMFORTIS (spinosad) is available in three sizes of chewable flavored tablets for oral administration to cats and kittens according to their weight. Each chewable flavored tablet is formulated to provide a minimum spinosad dosage of 22.5 mg/lb (50 mg/kg). Spinosad is a member of the spinosyns class of insecticides, which are non-antibacterial tetracyclic macrolides. Spinosad contains two major factors, spinosyn A and spinosyn D, derived from the naturally occurring bacterium, Saccharopolyspora spinosa . Spinosyn A and spinosyn D have the chemical compositions 2-[(6-deoxy-2,3,4-tri-O-methyl-α-L-mannopyranosyl)oxy]-13-[[5-(dimethylamino)tetrahydro-6-methyl-2H-pyran-2-yl]oxy]-9-ethyl-2,3,3a,5a,5b,6,9,10,11,12,13,14,16a,16b-tetradecahydro-14-methyl-1H-as-indaceno[3,2-d]oxacyclododecin-7,15-dione and 2-[(6-deoxy-2,3,4-tri-O-methyl-α-L-mannopyranosyl)oxy]-13-[[5-(dimethylamino)tetrahydro-6-methyl-2H-pyran-2-yl]oxy]-9-ethyl-2,3,3a,5a,5b,6,9,10,11,12,13,14,16a,16b-tetradecahydro-4,14-dimethyl-1H-as-indaceno[3,2-d]oxacyclododecin-7,15-dione, respectively.

Storage

Store at 20 to 25°C (68 to 77°F), excursions permitted between 15 to 30°C (59 to 86°F).

FDA adverse event reports

The FDA Center for Veterinary Medicine publishes the adverse event reports it receives through openFDA. The counts below are the reports naming spinosad as an active ingredient for each species this label names, as returned on 2026-09-16, coded by the VeDDRA reaction term the reporter chose. Reactions are counted per report, so one report can appear under several terms.

These are counts, not rates. Reporting is voluntary, the number of animals treated is not known, and a widely used product accumulates reports for that reason alone. A report records that an event followed a dose; it does not establish that the product caused it. The counts say nothing about how one product compares with another.