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MERCK Tri-Heart Plus Chewable Heartworm Dog Tablet - Pork

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IB# 107179
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Veterinary Diet Item

MERCK Tri-Heart Plus Chewable Heartworm  Dog Tablet - Pork
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MERCK Tri-Heart Plus is a chewable, pork flavored tablet administered once a month to protect your dog from the threat of potentially deadly heartworm disease, it also controls against roundworms and hookworms when given every month.

Dogs six months of age and older should be tested for heartworm disease prior to being put on a preventive program and tested annually thereafter. 



  • Once a month pork flavored chewable treat that is highly palatable
  • When given at the recommended dose and regimen, Tri-Heart Plus is effective against the tissue larval stage of heartworm larvae for a month after infection resulting in the prevention of adult heartworms
  • Treats and controls roundworms (T. canis, T. leonina) and hookworms (A. caninum, U. stenocephala, A. braziliense) once monthly when given routinely
  • Approved for dogs 6+ weeks of age, with no weight requirements



Tri-Heart Plus should be given orally as directed by your veterinarian. This medication should be administered at monthly (every 30 day) internally, year-round to guarantee protection from heartworms and to treat for roundworms and hookworms.  For dogs over 100 lbs, use the appropriate combination of chewables to ensure complete protection against heartworms.

Remove only 1 chewable at a time from the foil-backed blister card and return the card to the box to protect from light. Do not remove chewable from foil wrapper until you are ready to give it to your dog. Offer to the dog as a treat by hand or in a small amount of dog food. Tri-Heart Plus can be chewed and or swallowed whole. Make sure entire tablet is consumed. 

Missed Doses

Give the dose as soon as you remember, unless it is time for the next dose. Do not double dose.  If your dog has missed a dose please consult with your veterinarian as testing may be recommended sooner than usual.

Side Effects

Tri-Heart Plus is generally well tolerated in dogs. There are very few side effects when the drug is given at the usual dose. Ivermectin may cause a shock like reaction in dogs. If this occurs, notify your veterinarian. The following side effects have been reported with the use of Tri-Heart Plus: depression, lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia, staggering, convulsions, and hypersalivation.  Vomiting has been reported with pyrantel.

Other side effects may occur. If you notice anything unusual, contact your veterinarian.

Drug & Food Interactions

The following drugs can potentially interact with pyrantel pamoate: levamisole, organophospates, diethylcarbamazine, and piperazine.  Contact your veterinarian if your pet experiences any unusual reactions when different medications are given together. Make sure to tell your veterinarian what other medication you are giving to your pet. Quite often your veterinarian may prescribe two different medications, and a drug interaction may be anticipated. In this case, your veterinarian may vary the dose and/or monitor your pet more closely.


Certain dogs of the collie breed are more sensitive to the effects of ivermectin.

Heartworm testing should be performed prior to the start of prevention therapy. If the animal is off Tri-Heart Plus for 6 months or less, start the medication and test after 6 months since microfilaria, that take 6 months to mature, will result in a positive test result.

Allergic reactions to medications may occur. Be sure to inform VetSource and your veterinarian if your pet has any known drug sensitivities or allergies. If your pet displays symptoms of an allergic reaction, call your veterinarian immediately or go to a veterinary emergency clinic. Symptoms may include but are not limited to: swollen lips, tongue, face, airways; difficulty breathing; agitation; profuse salivation; vomiting; widespread hives and itching.

Adverse Reaction

If you are concerned that your pet has experienced an adverse reaction to this medication or you have concerns about the product, please contact the manufacturer, Merck, at 800-224-5318 or contact Vetsource customer service at 877-738-4443.


Store long term at 59-86 degrees F. Store in original packaging to protect from light.  Keep out of reach of children and pets.

IB# 107179

Active Ingredients:

ivermectin, pyrantel

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