Heartgard for Dogs

Heartgard for dogs is a chewable tablet administered monthly to prevent canine heartworm disease. This drug is approved by both the FDA and the EPA. The drug is also used for the control and treatment of other worm infections, such as hookworm and roundworm infections.


Heartgard should be given once a month throughout the year. It’s advisable to give it on the same date every month. Some vets recommend that the drug should only be given during mosquito season. In such cases, the drug should be given within 30 days of the dog’s first exposure to mosquitoes and within 30 days of its last exposure to mosquitoes. However, it’s best to administer the drug throughout the year. It’s important that the dog chew the drug and not swallow it. If a dog is habituated to swallowing his food, the tablet should be broken into pieces. In addition, care should also be taken to ensure that the dog ingests the complete dose. If the dog hasn’t consumed the complete dose, it’s safe to administer another dose with vet approval.

General Dosage Guidelines:

  • 68 mcg for dogs weighing 25 lbs.
  • 136 mcg for dogs weighing between 26 to 50 lbs.
  • 272 mcg for dogs weighing between 51 to 100 lbs.
  • A combination of tablets is administered to dogs weighing more than 100 lbs.

Ingredients Present in Heartgard and Heartgard Plus

Heartgard contains Ivermectin, and Heartgard Plus has two active ingredients, namely Ivermectin and Pyrantel pamoate. Both interfere with the parasite’s nerve transmission, thus causing paralysis and death.

Heartgard for Heartworm

Heartworm is a roundworm that’s spread through the bite of an infected mosquito. The parasite resides in the right ventricle of the heart of infected animals, hence its name. Heartgard is a prophylactic (preventive) drug that cannot reach the heart. It only kills the immature form of the heartworm that lives in the dog’s bloodstream, and not the adult worms that reside in the dog’s heart. Hence, it should be administered only to uninfected dogs. Heartgard can be administered to puppies over six weeks of age, and is also safe for pregnant or lactating dogs. Administration of the drug is relatively easy, as Heartgard is beef-flavored and palatable to pets. Research studies reveal that Heartgard has been shown to prevent infection in 99 percent of treated dogs.


  • It’s important to keep your vet informed about known allergies to any ingredients present in medication or to proteins like beef.
  • Heartgard medication shouldn’t be administered to pets more than once every 30 days. This is necessary to allow the dog to recover from melosomine dihydrochloride, a compound that may be toxic when administered in high amounts.
  • Heartgard should be stored at room temperature to protect it from extreme heat or cold. It should also be kept out of reach of pets and children.
  • This medication shouldn’t be given if your pet is prescribed other heartworm medication.
  • It’s important not to overdose the dog, as it might cause in-coordination, vomiting and diarrhea, tremors, dilated pupils and even death. 

Heartgard also acts on adult hookworms and roundworms and is effective in the elimination of intestinal infection. Pet owners should read and follow package instructions before administration of any medication. If in doubt, it’s important to talk with the vet about treatment options suited to individual pet health concerns.