Capstar vs Comfortis: what's the difference?
How Capstar and Comfortis compare: what each is for, how it works, side effects and cost, side by side.
Last updated: October 2026 · 2 sources · see sources
Side by side
| Capstar | Comfortis | |
|---|---|---|
| Generic name | Nitenpyram | Spinosad |
| Brand names | Capstar | Comfortis, Trifexis |
| For | Dogs and cats | Dogs and cats |
| Prescription | Over the counter (ask your vet first) | Prescription |
| Used for | A pill that kills adult fleas fast. It works for about a day, so it is used for quick knockdown, not long-term prevention. [1] | A monthly chewable that kills fleas in dogs and cats. [2] |
| How it works | It is absorbed quickly and kills fleas that bite. [1] | It overstimulates the flea's nervous system. [2] |
| Common side effects | Rare. Itching (as fleas die), vomiting, diarrhea, low appetite or energy changes. [1] | Vomiting, low appetite, diarrhea and drooling. [2] |
| Use with care | Not for pets under 2 pounds or 4 weeks old. [1] | Use caution in pets with seizures and pets taking ivermectin at high doses. [2] |
| Full guide | Capstar guide | Comfortis guide |
Key differences
- How you get them differs: Capstar is over the counter; Comfortis is prescription.
Which one is right for my pet?
That is a call for your vet. They weigh your pet's age, weight, other health problems, other medicines and what you can realistically give at home.
Switching from Capstar to Comfortis is common, but do it only with your vet's plan.
Common questions
What is the difference between Capstar and Comfortis?
Capstar kills adult fleas fast but only works for about a day; Comfortis is a monthly chew for ongoing flea control.
Is Capstar better than Comfortis?
Neither is better for every pet. Your vet chooses based on your pet's species, age, health history, other medicines and what you can manage at home.
Can my pet take Capstar and Comfortis together?
Only if your vet says so. Some medicines in the same family should not be combined, and others are often used together. Always check before adding or switching.
Do Capstar and Comfortis need a prescription?
Capstar: Many forms are sold without a prescription. Still, check with your vet first. Pet doses and safe products are not the same as for people. Comfortis: Yes. It needs a prescription from a veterinarian.
Related
This page is general information for planning, not veterinary advice. Talk to your vet about your own pet.