Heartgard vs Heartgard Plus

When it comes to protecting our furry friends from heartworms, pet owners are presented with various options. Among the numerous heartworm preventatives available in the market, Heartgard and Heartgard Plus are two popular choices. However, despite their similar names, these products have distinct differences that pet owners should be aware of.

Introduction to Heartgard and Heartgard Plus

Heartgard and Heartgard Plus are monthly oral medications designed to prevent heartworm disease in dogs. They are both produced by Boehringer Ingelheim, a global pharmaceutical company, ensuring their reliability and effectiveness.

Heartgard (Ivermectin)

  • Active Ingredient: Ivermectin
  • Purpose: Prevents heartworm disease
  • Coverage: Only targets heartworm larvae

Heartgard Plus (Ivermectin + Pyrantel Pamoate)

  • Active Ingredients: Ivermectin and Pyrantel Pamoate
  • Purpose: Prevents heartworm disease, and treats and controls roundworms and hookworms
  • Coverage: Targets heartworm larvae, roundworms, and hookworms

Key Differences

While both products aim to prevent heartworm disease, their key differences lie in their formulation and the range of parasites they target.

Range of Parasites Covered

  • Heartgard: Specifically designed to prevent heartworm disease by targeting the larvae stage of the heartworm.
  • Heartgard Plus: Apart from preventing heartworm disease, it also treats and controls roundworms and hookworms, thanks to the addition of Pyrantel Pamoate.


  • Heartgard: Contains only Ivermectin.
  • Heartgard Plus: A combination of Ivermectin and Pyrantel Pamoate, providing a broader spectrum of protection against parasites.

Comparative Table Chart

Features / Product Heartgard Heartgard Plus
Active Ingredients Ivermectin Ivermectin + Pyrantel Pamoate
Purpose Prevents heartworm disease Prevents heartworm disease, treats and controls roundworms and hookworms
Coverage Heartworm larvae Heartworm larvae, roundworms, hookworms
Manufacturer Boehringer Ingelheim Boehringer Ingelheim
Dosage Form Chewable Chewable
Frequency Monthly Monthly

Why Choose One Over the Other?


  • Best For: Dogs in areas with a low risk of roundworms and hookworms, or for pet owners looking for a heartworm-specific preventative.
  • Pros: Focuses specifically on preventing heartworm disease.
  • Cons: Does not cover roundworms or hookworms.

Heartgard Plus

  • Best For: Dogs in areas where roundworms and hookworms are prevalent, providing an all-encompassing protection.
  • Pros: Broader protection against a variety of parasites.
  • Cons: Slightly more expensive than Heartgard.

Making the Right Choice

When it comes to deciding between Heartgard and Heartgard Plus, it’s crucial to consider your geographical location, your dog’s lifestyle, and any recommendations from your veterinarian. Both products are highly effective when administered monthly, and ensuring consistent protection is key to keeping your dog healthy and happy.


In the showdown of Heartgard vs. Heartgard Plus, there is no one-size-fits-all answer. It ultimately depends on your dog’s specific needs and your personal preference as a pet owner. By understanding the key differences between these two products, you can make an informed decision and ensure that your furry friend is protected against heartworm and other parasites.

Frequently Asked Questions

Q1: Can I Switch from Heartgard to Heartgard Plus without a Veterinarian Consultation?

A1: While both products are from the same manufacturer and have Ivermectin as a common ingredient, they serve different purposes. Heartgard Plus includes an additional ingredient to combat roundworms and hookworms. Before making any changes to your pet’s medication regimen, consult with your veterinarian to ensure it’s a safe and beneficial switch for your specific pet’s health needs.

Q2: Are There Any Side Effects Associated with Heartgard or Heartgard Plus?

A2: Both medications are generally well-tolerated by dogs. However, as with any medication, there’s a potential for side effects. Common side effects might include vomiting, diarrhea, or lethargy. In rare cases, particularly with dogs that have the MDR1 gene mutation (common in breeds like Collies and Australian Shepherds), severe reactions including seizures, tremors, or even death could occur. Always observe your dog closely after administering any medication and report any adverse reactions to your veterinarian immediately.

Q3: How Do I Know if My Dog Needs Protection Against Roundworms and Hookworms?

A3: Roundworms and hookworms are common intestinal parasites in dogs, and they can pose serious health risks. Dogs can contract these parasites from contaminated soil, water, feces, or from their mother during birth or nursing. If your dog has a history of intestinal parasites, lives in or frequents contaminated environments, or has clinical signs of parasitic infection (such as diarrhea, vomiting, weight loss, or visible worms in the feces), a broader spectrum of protection like Heartgard Plus may be recommended.

Q4: Is Heartgard Plus More Expensive Than Heartgard?

A4: Yes, generally speaking, Heartgard Plus tends to be slightly more expensive than Heartgard. This is because Heartgard Plus offers a broader spectrum of protection against additional parasites. When considering the cost, weigh the benefits of broader protection and potential savings on treating parasite infections separately against the higher upfront cost.

Q5: Can I Use Heartgard or Heartgard Plus for My Puppy?

A5: Yes, both Heartgard and Heartgard Plus are safe for puppies as young as six weeks old. The correct dosage depends on your puppy’s weight, so it’s crucial to have your puppy weighed accurately to ensure they receive the proper dose. Regular preventive care starting from a young age is vital to protect them from heartworm and other parasitic infections as they grow.

Q6: How Do Heartgard and Heartgard Plus Work to Prevent Heartworm Disease?

A6: Both medications work by interfering with the nervous system of the heartworm larvae, leading to their paralysis and eventual death. The key ingredient, Ivermectin, is a broad-spectrum antiparasitic that targets the larvae during the early stages of their life cycle, preventing them from maturing into adult heartworms. The addition of Pyrantel Pamoate in Heartgard Plus also paralyzes roundworms and hookworms, providing additional protection.

Q7: How Effective Are Heartgard and Heartgard Plus in Preventing Heartworm Disease?

A7: When administered monthly, as directed, both Heartgard and Heartgard Plus are over 99% effective in preventing heartworm disease. Consistency is crucial, as missing doses can leave your dog vulnerable to infection. If a dose is missed, consult your veterinarian for guidance on how to proceed and to discuss whether heartworm testing is necessary.

Q8: Can Heartgard or Heartgard Plus Be Given to a Dog Already Infected with Heartworms?

A8: Administering heartworm preventatives to a dog already infected with adult heartworms can lead to severe reactions and is not recommended. If your dog tests positive for heartworms, your veterinarian will recommend a different treatment protocol to address the infection. Always ensure your dog is tested for heartworms before starting any preventive medication.

Q9: What Happens If I Accidentally Give My Dog a Double Dose of Heartgard or Heartgard Plus?

A9: While both medications have a wide margin of safety, an overdose can still be harmful. Signs of overdose might include vomiting, diarrhea, incoordination, dilated pupils, or tremors. If you suspect you’ve given your dog a double dose, contact your veterinarian or an emergency animal poison control hotline immediately.

Q10: Can Cats Take Heartgard or Heartgard Plus?

A10: Heartgard and Heartgard Plus are formulated specifically for dogs. Cats require a different formulation, and there is a feline version of Heartgard available. Never give your cat dog-specific medication without consulting your veterinarian, as this can lead to severe reactions or death.

Q11: Is Monthly Administration of Heartgard or Heartgard Plus Necessary Year-Round?

A11: The American Heartworm Society recommends year-round prevention for heartworm disease, regardless of where you live. Heartworms are transmitted by mosquitoes, and because weather patterns can be unpredictable, mosquitoes can be present even during months we traditionally consider to be “off-season” for them. Administering Heartgard or Heartgard Plus monthly, throughout the entire year, ensures consistent protection for your dog, reducing the risk of heartworm infection.

Q12: What Should I Do If My Dog Vomits After Taking Heartgard or Heartgard Plus?

A12: If your dog vomits within an hour of administration, the full dose may not have been absorbed into their system. In this case, it’s generally safe to give another full dose. However, if your dog has a history of reactions to the medication, or if they continue to vomit, contact your veterinarian before re-dosing. Consistency in prevention is key, so addressing any issues with tolerability as soon as they arise helps maintain your dog’s protective regimen.

Q13: Can I Purchase Heartgard or Heartgard Plus Without a Prescription?

A13: Both Heartgard and Heartgard Plus are prescription medications, meaning they require approval from a veterinarian before they can be dispensed. This ensures that your dog is appropriately tested for heartworm disease before starting the medication, as giving heartworm preventatives to a dog with an active heartworm infection can lead to severe complications. Your veterinarian will also ensure that the medication is appropriate for your dog’s health status and lifestyle.

Q14: Are There Any Breeds That Should Not Take Heartgard or Heartgard Plus?

A14: Dogs with a mutation in the MDR1 gene (Multi-Drug Resistance 1), which includes breeds such as Collies, Shetland Sheepdogs, and Australian Shepherds, can be more sensitive to the effects of ivermectin, the active ingredient in Heartgard and Heartgard Plus. However, the dosage of ivermectin in these preventatives is generally considered safe even for breeds with the MDR1 mutation. Regardless, it’s crucial to consult with your veterinarian, as they will consider your dog’s breed, health status, and any potential genetic factors when recommending a heartworm preventative.

Q15: How Do I Choose Between Heartgard and Heartgard Plus for My Dog?

A15: The choice between Heartgard and Heartgard Plus should be based on your dog’s specific health needs and the parasite risks in your area. Heartgard provides protection against heartworms alone, while Heartgard Plus also protects against roundworms and hookworms. Discuss with your veterinarian about the prevalence of these parasites in your area and any specific health concerns for your dog. They can provide guidance on which product is more suitable for your dog’s preventive care regimen.

Q16: Can Human Error Affect the Effectiveness of Heartgard or Heartgard Plus?

A16: Yes, human error in administration can affect the effectiveness of these medications. Giving the medication inconsistently (skipping months), administering the wrong dosage, or failing to ensure the dog consumes the entire dose can leave your dog unprotected. Establishing a routine, using reminders, and closely observing your dog while they take their medication can help mitigate these risks.

Q17: How Does the Cost of Heartgard and Heartgard Plus Compare to Other Heartworm Preventatives?

A17: The cost of Heartgard and Heartgard Plus is generally competitive with other heartworm preventatives on the market. However, because Heartgard Plus offers broader protection against additional parasites, it may be slightly more expensive than Heartgard. When considering cost, also consider the potential savings in not having to treat parasitic infections separately and the peace of mind that comes with comprehensive protection.

Q18: Can Heartgard or Heartgard Plus Be Given Alongside Other Medications?

A18: Heartgard and Heartgard Plus are safe to use alongside many other medications. However, always inform your veterinarian about any other medications, supplements, or treatments your dog is receiving. They can provide guidance and ensure that there are no potential interactions or contraindications.

Q19: Are There Any Situations Where Heartgard or Heartgard Plus Should Not Be Administered?

A19: Do not administer Heartgard or Heartgard Plus to dogs that have tested positive for adult heartworms. Additionally, if your dog has a known sensitivity to ivermectin or the other ingredients in these medications, they should not be used. In these cases, your veterinarian can recommend alternative methods of heartworm prevention and treatment.

Q20: How Should Heartgard and Heartgard Plus Be Stored?

A20: Both Heartgard and Heartgard Plus should be stored at room temperature, away from direct sunlight and moisture. Keeping the medication in its original packaging until use helps protect it from environmental factors that could degrade its effectiveness. Always check the expiration date before administering, and do not use the medication if it has expired.

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