Tri-Heart Plus vs Heartgard Plus - Which Heartworm Medication Is Best for Your Dog?

Tri-Heart Plus vs Heartgard Plus - Which Heartworm Medication Is Best for Your Dog?

Edward Simmons
Protecting your dog from parasites isn’t just about avoiding vet bills; it’s about safeguarding their life. Heartworms, roundworms, and hookworms can cause serious harm if left untreated, and with so many preventatives on the market, pet owners are often left asking: 

Which dog heartworm preventives work best—and what’s the difference between them?

If you’ve been comparing Heartgard Plus vs Tri-Heart Plus, you’ve probably also heard of alternatives like Interceptor Plus, Sentinel, or even topical solutions like Revolution. 

📌 TL;DR – Tri-Heart Plus vs Heartgard Plus

  • Both contain the same active ingredients: ivermectin and pyrantel
  • Offer identical protection against heartworms, roundworms, and hookworms
  • Heartgard Plus is a premium brand with a beef-flavored chew
  • Tri-Heart Plus is a more affordable alternative with similar effectiveness
  • Choose based on budget, taste preference, and your vet’s guidance

While all of these medications offer some level of protection, Heartgard Plus and Tri-Heart Plus remain two of the most widely recommended options due to their proven effectiveness, affordability, and broad-spectrum coverage

At HardyPaw, we specialize in helping pet parents compare trusted preventatives like Heartgard Plus vs Tri-Heart Plus, giving you the clarity to protect your dog without unnecessary expense or confusion.

Tri-Heart Plus vs Heartgard Plus: Overview and Ingredients

Heartgard Plus is a monthly prescription medication manufactured by Boehringer Ingelheim. It contains ivermectin and pyrantel, two powerful antiparasitic agents that work together to prevent heartworm disease and treat existing roundworm and hookworm infections. 

The medication is delivered in a soft, beef-flavored chewable tablet that most dogs readily accept, making dosing stress-free for both pets and owners.

On the other hand, Tri-Heart Plus, produced by Merck Animal Health, offers the same active ingredients - ivermectin and pyrantel, and the same monthly dosing schedule. 

Like Heartgard Plus, it protects dogs from heartworms, roundworms, and hookworms. Tri-Heart Plus is also a chewable tablet, though it’s often considered a budget-friendly alternative for pet owners looking to cut costs without sacrificing protection quality.

Verdict: While both medications deliver nearly identical protection and composition, the decision between them often comes down to brand familiarity, price sensitivity, or your veterinarian’s recommendation.

Key Differences Between Heartgard Plus and Tri-Heart Plus

The main difference between Heartgard Plus and Tri-Heart Plus is brand positioning and cost. Both contain the same active ingredients—ivermectin and pyrantel—and offer identical protection against heartworms, roundworms, and hookworms. However, Heartgard Plus is marketed as a premium option with a beef-flavored chew that appeals to picky dogs. Tri-Heart Plus offers the same protection at a lower price, making it ideal for budget-conscious pet owners.

Although Heartgard Plus and Tri-Heart Plus are medically equivalent in their protection, a few practical differences can influence your decision as a dog owner.

  • Brand Positioning: Heartgard Plus is considered a premium product by Boehringer Ingelheim, while Tri-Heart Plus is marketed as a value-focused alternative from Merck Animal Health.
  • Palatability Experience: Many dog owners report Heartgard Plus’s beef-flavored chew is more appealing to picky eaters, whereas Tri-Heart Plus, though effective, is less favored in terms of taste.
  • Price-to-Value Perception: The difference often comes down to cost versus convenience. Some owners prefer paying slightly more for stronger brand trust and flavor assurance; others prioritize affordability with similar results.

These real-world differences, though subtle, can impact adherence and long-term satisfaction.

To simplify your comparison, let’s break these points into a quick-reference table so you can evaluate features at a glance.

Tri-Heart Plus vs Heartgard Plus - Comparison Table

Both options offer nearly identical formulations and coverage, with no significant difference in safety profile or administration method. The real differentiators often lie in brand perception, flavor, and cost.

In the next section, we’ll take a closer look at pricing differences—a key factor for many pet parents choosing between the two.

How Much Does Heartgard Plus vs Tri-Heart Plus Cost?

The average cost of Heartgard Plus Chew is approximately $12 to $15 per month. Whereas the average cost of Tri-Heart Plus Chewable Tablet is approximately $9.39 per month

Here is the detailed pricing breakdown of Heartgard Plus vs Tri-Heart Plus

Heartgard Plus Chew (Price per tablet):

Tri-Heart Plus Chewable Tablet (6-month packs):

Factors That Influence Heartworm Medication Cost

  • Dog Size: Larger dogs require higher dosages and cost more.
  • Pack Size: Buying single doses (Heartgard) offers flexibility; bulk packs (Tri-Heart) reduce price per dose.
  • Retailer & Shipping: Prices vary across vets, pharmacies, and online stores, especially with shipping or regional markups.

Overall, Tri-Heart Plus Chewable Tablet is more affordable for those able to buy in bulk, while Heartgard Plus Chew offers trusted brand recognition and flexible monthly purchase options.

Next, let’s explore what side effects you should watch for with each medication.

What Are the Side Effects of Heartgard Plus and Tri-Heart Plus in Dogs?

Both Heartgard Plus Chew and Tri-Heart Plus Chewable Tablet are considered safe and effective. Still, as with any heartworm medication, some dogs may experience side effects. Knowing what to expect—and when to contact your vet—can give you peace of mind.

Heartgard Plus Side Effects in Dogs

Heartgard Plus Chew, containing ivermectin and pyrantel, is generally well tolerated. However, a small percentage of dogs may show mild reactions shortly after dosing:

  • Vomiting
  • Diarrhea or soft stools
  • Temporary lethargy
  • Lack of appetite

Rare but more serious side effects of Heartgard Plus may include:

  • Seizures
  • Disorientation
  • Swelling or allergic reactions (especially in ivermectin-sensitive breeds)

Note: Breeds with the MDR1 gene mutation, such as Collies or Australian Shepherds, may be more prone to ivermectin sensitivity.

Tri-Heart Plus Side Effects in Dogs

Like its counterpart, Tri-Heart Plus Chewable Tablet also contains ivermectin and pyrantel, meaning the potential side effects are nearly identical:

  • Mild gastrointestinal upset (vomiting, diarrhea)
  • Lethargy
  • Reduced appetite

Though uncommon, serious side effects from Tri-Heart Plus may include:

  • Neurological symptoms (e.g., tremors, seizures)
  • Allergic skin reactions or swelling

These side effects are rare but should be monitored closely, especially if your dog is starting this medication for the first time.

When to Call Your Vet for Side Effects?

Contact your veterinarian if:

  • Mild symptoms persist beyond 24 hours
  • You notice serious symptoms like seizures, swelling, or disorientation
  • You suspect a dosage error
  • You are switching medications and see new reactions

Coming up: We’ll guide you on how to safely switch between Heartgard Plus and Tri-Heart Plus without risking a gap in heartworm protection.

Is It Safe to Switch from Heartgard Plus to Tri-Heart Plus (or Vice Versa)?

Yes, switching between Heartgard Plus for dogs and Tri-Heart Plus for dogs is generally safe because both contain the same active ingredients—ivermectin and pyrantel—and provide identical protection against heartworms, roundworms, and hookworms. 

However, individual tolerance, medical history, or breed-specific drug sensitivities (like the MDR1 gene mutation) should be evaluated before making a change.

How to Switch Heartworm Medications Without Gaps?

To safely switch heartworm preventatives:

  • Maintain monthly dosing without missing a cycle.
  • If switching from Heartgard Plus to Tri-Heart Plus, begin the new tablet exactly 30 days after the last Heartgard Plus dose.
  • Ensure you're using the correct Tri-Heart Plus dosage for your dog’s weight class to maintain consistent efficacy.
  • Avoid using both medications together or overlapping doses, as it offers no additional protection and could increase risk of side effects.

Skipping even one month can give heartworm larvae time to mature—leading to potentially life-threatening infection.

Should You Talk to a Vet Before Switching Heartworm Medications?

Absolutely. Your veterinarian can:

  • Confirm if switching from Heartgard Plus Chewables to Tri-Heart Plus Chewable Tablets is suitable based on your dog’s health and history.
  • Help you monitor your dog for any adverse reactions after the switch.
  • Ensure continuity of care, especially for dogs with other conditions or breed-specific sensitivities to ivermectin.

Vet approval is also critical if you want to maintain eligibility for manufacturer guarantees tied to heartworm prevention effectiveness.

Coming up next, we’ll answer a key question: Can Heartgard Plus and Tri-Heart Plus be alternated—or even used together?

Can You Alternate Between Heartgard Plus and Tri-Heart Plus Each Month?

Yes, alternating between Heartgard Plus Chew and Tri-Heart Plus Chewable Tablet is generally safe because both contain the same active ingredients. From a clinical perspective, the protective effect remains unchanged as long as:

  • You administer only one tablet per month
  • You don’t skip or delay doses
  • You stay within the correct weight-based dosage for your dog

However, frequent switching is not typically advised unless guided by a veterinarian. Maintaining consistency in brand and dosage reduces the risk of owner confusion and dosing errors.

Is Monthly Alternation Between Heartworm Medications Safe?

No, using Heartgard Plus and Tri-Heart Plus together is not recommended. Since they contain identical active ingredients, giving both could result in an overdose of ivermectin and pyrantel, potentially increasing the risk of side effects such as:

  • Tremors
  • Vomiting
  • Lethargy
  • Neurological symptoms (especially in sensitive breeds)

Stick to one heartworm medication per monthly cycle to ensure safety and maintain proper dosage.

Veterinarian Recommendations for Heartworm Medication

Most veterinarians recommend:

  • Sticking to one trusted product consistently, whether that’s Heartgard Plus or Tri-Heart Plus
  • Only switching or alternating when necessary (e.g., availability issues, pricing concerns)
  • Always consulting your vet before making any changes to your dog’s heartworm medication routine

While both brands are equally effective, consistency supports better compliance, safety, and record-keeping.

Which Heartworm Medication Is Right for Your Dog - Heartgard Plus or Tri-Heart Plus?

When comparing Heartgard Plus vs Tri-Heart Plus, the reality is this: both offer effective, vet-approved protection against heartworms, roundworms, and hookworms. They share the same active ingredients, dosage schedule, and safety profile.

  • Choose Heartgard Plus if your dog is a picky eater and you value premium branding with a palatable beef-flavored chew.
  • Choose Tri-Heart Plus if you're looking for a more budget-conscious alternative with equivalent parasite protection.

Ultimately, the best heartworm medication depends on your dog’s needs, your budget, and your veterinarian’s advice.

Order Trusted Heartworm Protection from HardyPaw

At HardyPaw, we help you make smart, confident choices when it comes to parasite prevention. Whether you decide on Heartgard Plus or Tri-Heart Plus, our team is here to ensure your pet stays protected—all year long.

👉 Explore your options and order your heartworm preventatives now at HardyPaw.com — because your dog’s health deserves nothing less than love and care.

Common Questions About Heartgard Plus and Tri-Heart Plus

Is Heartgard Plus safe for pregnant or nursing dogs?

Yes, Heartgard Plus is considered safe for use in pregnant and lactating dogs, but always consult your veterinarian before administering it.

Can you buy Heartgard Plus or Tri-Heart Plus without a prescription?

No, both medications require a prescription from a licensed veterinarian in the United States for legal purchase.

How quickly does Heartgard Plus start working after giving it?

Heartgard Plus begins eliminating heartworm larvae within 24 to 48 hours of administration.

What should I do if I forget to give my dog a dose of heartworm medication?

Give the missed dose as soon as possible. If it’s been over 30 days, consult your vet and consider heartworm testing before continuing.

Can Heartgard Plus be used to treat active heartworm infections?

No, Heartgard Plus is a preventative and does not treat dogs that already have heartworm disease.

Do Heartgard Plus or Tri-Heart Plus protect against fleas or ticks?

Neither Heartgard Plus nor Tri-Heart Plus provide flea or tick protection. You’ll need a separate product for external parasites.

Are allergic reactions possible with these heartworm medications?

Yes, although rare, some dogs may have allergic reactions like swelling, hives, or difficulty breathing and require immediate veterinary care.

Are there natural alternatives to Heartgard Plus for heartworm prevention?

While some natural remedies exist, none are clinically proven or FDA-approved. Always discuss alternatives with your veterinarian.

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