Heartgard Plus vs Interceptor

Learn similarities and differences between Heartgard Plus and Interceptor. While both medications are designed to control parasites, particularly heartworm, both prescription medications offer differing levels of protection. They also contain different active ingredients and therefore have different side effects.

Heartworm is spread from by infected mosquitoes. Studies find that dogs infected with heartworm that never receive treatment have a lifespan of 5 to 7 years. By ensuring your dog takes monthly heartworm medications, you can prevent this devastating disease.

Parasite Prevention Offered by Heartgard Plus and Interceptor

Heartgard Plus and Interceptor do not prevent fleas and ticks. If you need flea and tick prevention, you'll need another medication. They do work to kill and prevent heartworm and other parasitic worms.

Heartgard offers complete protection from heartworm, hookworm and roundworms. They do not offer protection against whipworm however. Interceptor does offer protection from whipworm, but only partial protection from hookworm. There is some evidence that Interceptor also treats demodectic mange infections. Neither medication protects against tapeworm.

Both are Chewable Medications

Both Heartgard and Interceptor are beef-flavored chewable medications. You give the dog the chewable tablet once a month. In terms of cost, both average about $5 per chewable.

Heartgard Plus comes in three dosages. The tablets in the blue package are meant for dogs up to 25 pounds. Dogs weighing 25 to 50 pounds need the green package. Finally, dogs 51 to 100 pounds need the brown package. If your dog weighs more than 100 pounds, you'll need to combine packages to get the right dosage. For example, if your dog weighed 115 pounds, you'd need to give him a tablet from the blue package and the brown package.

Interceptor also comes in four dosages. The brown package is correct for dogs weighing up to 10 pounds. The green package is for dogs weighing 11 to 25 pounds. The yellow package is for dogs weighing 26 to 50 pounds. Finally, the weight package is for dogs over 50 pounds.

There is no generic version of Interceptor. However, Heartgard does have a generic version called Tri-Heart Plus that costs approximately 40 percent less than the brand name medication.

Differences Between Active Ingredients and Common Side Effects

Heartgard Plus uses a blend of ivermectin and pyrantel to kill and protect against parasitic worms. You should not give the medication to puppies six weeks or younger. Ivermectin is linked to toxic reactions in specific breeds of dogs. The list of dogs affected by ivermectin include:

  • Australian Shepherds

  • Collies

  • Sheepdogs

If you have a purebred or mix consisting of at least one of the listed breeds, it may be safer to avoid using Heartgard. If you do use it, watch closely for toxicity. Signs of a drug reaction include:

Interceptor's active ingredient is milbemycin oxime. Milbemycin oxime appears to be safe for all breeds, so you don't have to worry if you have an Australian Shepherd, Collie or Sheepdog. While side effects are rare, you should watch for:

  • Depression

  • Disorientation

  • Drooling

  • Seizures

  • Vomiting

  • Weakness

Milbemycin is not safe in puppies under four weeks of age. Your dog should be tested for heartworm first. Shock-like symptoms can occur if the dog has an active heartworm infection.