Interceptor vs Heartgard

Updated on February 03, 2023
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Reviewed by Dr. Elyse Macartney
DVM
dog & cat with vets
Features Interceptor Heartgard
Primary usage

Dogs: Prevents heartworm caused by Dirofilaria immitis. Protects against hookworm, roundworm and whipworm. Controls adult hookworm infections. Eliminates adult roundworm and whipworm infections. 

Cats: Indicated for use in the prevention of heartworm disease caused by Dirofilaria immitis, and the removal of adult hookworms and roundworms.

Dog: Prevents heartworm infection caused by Dirofilaria immitis

Cats: Prevents heartworm infection. Also removes and controls infections of hookworms in cats (Ancylostoma tubaeforme and A. brasiliense).
Exta-label usage Treats mite infestations in dogs

Treats demodectic mange, scabies, ear mites, hookworms, roundworms and capillaria.

In cats, it may be used to treat ear mites and feline scabies.
Available forms Tablet Tablet
Active ingredient Milbemycin oxime Ivermectin
Takes effect 1 to 2 days for internal parasites 1 to 2 hours
Approved for

Dogs 4 weeks and older and 2 lbs. or heavier

Cats 6 weeks and older and 1.5 lbs. or heavier

Dogs 6 weeks and older

Cats 6 weeks and older
Monthly dosage guidelines

Dogs:

  • 2 to 10 Ibs. = 1 tablet (2.3 mg)
  • 11 to 25 Ibs. =1 tablet (5.75 mg)
  • 26 to 50 Ibs. = 1 tablet (11.5 mg)
  • 51 to 100 Ibs. = 1 tablet (23.0 mg)

Cats:

  • 1.5 to 6 lbs. = 1 tablet (5.75 mg)
  • 6.1 to 12 lbs. = 1 tablet (11.5 mg)
  • 12.1 to 25 lbs. = 1 tablet (23.0 mg)

Dogs:

  • Up to 25 lbs. = 1 tablet (68 mcg)
  • 26 to 50 lbs. = 1 tablet (136 mcg)
  • 51 to 100 lbs. = 1 tablet (272 mcg)

Cats:

  • Up to 5 lbs. = 1 tablet (55 mcg)
  • 6 to 15 lbs. = 1 tablet (165 mcg)
Prescription required? Yes Yes
How it works Chemical derivative of microorganisms found in the soil, from the genus Streptomyces. Anthelmintic activity results from interference with invertebrate neurotransmission. Chemical derivative of microorganisms found in the soil, from the genus Streptomyces. Anthelmintic activity results from interference with invertebrate neurotransmission.
Directions for use

Dogs: Give orally once a month at the recommended minimum dosage rate of 0.23 mg per pound of body weight, with or without food.

Cats: Give orally once a month, at the recommended minimum dosage rate of 0.9 mg per pound of body weight, with or without food.

Dogs and cats: Give orally once a month with or without food
Recommended for pregnant or nursing dogs? Safety for pregnant and nursing dogs is unknown. Use with caution. Yes
Side effects Depression, lethargy, vomiting, ataxia, anorexia, diarrhea, convulsions, weakness and hypersalivation

Stomach upset, vomiting, diarrhea, dilated pupils, unsteadiness and dazed demeanor.

Neurological side effects may be seen when given in high doses; may also cause shock in high doses.

Adverse reactions at lower doses seen in Collie and Sheep breeds of dogs.
Adverse drug interactions Cyclosporine, amiodarone, diltiazem, azole antifungals and erythromycin Ketoconazole, itraconazole, cyclosporine, erythromycin, amlodipine besylate and nifedipine
Heartworm test required before taking? Yes Yes
Breed considerations Monitor and potentially screen breeds with possible sensitivities, including Collies, Sheepdogs and Collie and Sheepdog crossbreeds. Monitor and potentially screen breeds with possible sensitivities, including Collies, Sheepdogs and Collie and Sheepdog crossbreeds. 

FAQs About Interceptor vs. Heartgard

Does Heartgard prevent whipworms?

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No, Heartgard does not prevent whipworms. If you are looking for whipworm medicine for dogs, ask your vet about Interceptor Plus for dogs or another recommendation. 

What is the difference between Interceptor and Heartgard?

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The chart above lists many similarities and differences between Interceptor vs. Heartgard. The primary difference between the two medicines is that Interceptor helps prevent or treat several conditions, including heartworms. Heartgard is primarily used only to prevent heartworms, though it can be used off-label to treat other conditions. 

Where can I get heartworm medicine for my dog?

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Many heartworm medicines for dogs require a prescription, so your first stop will be your vet’s office. After receiving authorization, you can have it filled at your vet’s office or most pet pharmacies. At Petco, our pharmacy fulfilled by Vetsource can fill many prescriptions, including Heartgard Plus, other heartworm medicines and dewormer treatments. 

Is heartworm medicine necessary for dogs?

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The American Heartworm Society recommends that all dogs receive year-round heartworm prevention treatment. Previously, heartworms were rarely seen in certain parts of the country, but cases have now been reported in all 50 states. Dogs contract heartworms from infected mosquitos. The parasite Dirofilaria immitis will live and breed inside an infected dog’s lungs and heart and can grow up to 12 inches long. If left untreated, heartworms can cause lung, organ and heart damage by blocking blood vessels. Eventually, heartworm infection can be fatal. Ultimately, it is up to you to determine if you feel your pet should receive heartworm medicine for dogs. Keep in mind that it’s much easier to prevent heartworms than to cure an active infection. Consult your veterinarian for more information on heartworm medicine for dogs. 

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