Ivermectin vs Interceptor: what's the difference?
How Ivermectin and Interceptor compare: what each is for, how it works, side effects and cost, side by side.
Last updated: October 2026 · 3 sources · see sources
Side by side
| Ivermectin | Interceptor | |
|---|---|---|
| Generic name | Ivermectin | Milbemycin oxime |
| Brand names | Heartgard, Heartgard Plus, Tri-Heart | Interceptor, Sentinel, Trifexis |
| For | Dogs and cats | Dogs and cats |
| Prescription | Prescription | Prescription |
| Used for | Mainly a monthly heartworm preventive. Vets also use it for mites and some worms. [1] | Prevents heartworm and treats hookworms and roundworms. Some combinations also control fleas. [2] |
| How it works | At preventive doses it kills young heartworm larvae before they can grow into adult worms. [1] | It kills heartworm larvae and some intestinal worms by acting on their nerves. [2] |
| Common side effects | Well tolerated at heartworm-prevention doses. Higher doses can cause wobbliness, tremors, dilated pupils and drooling. [1] | Well tolerated at regular doses. Higher doses can cause weakness, wobbliness and drooling. [2] |
| Use with care | Collies, sheepdogs and related breeds can be very sensitive at high doses (MDR1 gene). Dogs need a negative heartworm test first. [1] | Dogs need a negative heartworm test before starting. [2] |
| Typical price | Monthly heartworm preventive, as listed on owner bills: $6–$18 a dose [3] | Monthly heartworm preventive, as listed on owner bills: $6–$18 a dose [3] |
| Full guide | Ivermectin (Heartgard) guide | Interceptor guide |
Key differences
On the basics they are alike: same kind of animal, same way to get them. The differences are in how they work and what else they cover, shown in the table above.
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 Ivermectin to Interceptor is common, but do it only with your vet's plan.
Common questions
What is the difference between Ivermectin and Interceptor?
Both are monthly heartworm preventives. Interceptor also treats hookworms and roundworms on its own; Heartgard's ivermectin is also used for mites.
Is Ivermectin better than Interceptor?
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 Ivermectin and Interceptor 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 Ivermectin and Interceptor need a prescription?
Ivermectin: Yes. It needs a prescription from a veterinarian. Interceptor: Yes. It needs a prescription from a veterinarian.
How much do Ivermectin and Interceptor cost?
Ivermectin: Monthly heartworm preventive, as listed on owner bills $6–$18 a dose. Interceptor: Monthly heartworm preventive, as listed on owner bills $6–$18 a dose. Prices vary by pet size, pharmacy and clinic.
Related
This page is general information for planning, not veterinary advice. Talk to your vet about your own pet.