Tri-Heart Plus Oral Heartworm Preventive by Merck
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Tri-Heart® Plus Chewables by Merck

RX - Tri-Heart Plus Chewable Tablets 68mcg ivermectin/57mg pyrantel (1-25 lb dogs)
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51-100 lb dogs
12 ct
$6.14 each    $6.14 each
How many 12 cts?
6 ct
$6.49 each    $6.14 each
How many 6 cts?
$7.49 each
   $6.14 each
How many Chewables?
Total Qty: 1 x 1 = 1
Price Per Chewable: $7.49
Subtotal: $7.49
Add to Cart
All items In-Stock and ready for delivery unless otherwise noted
26-50 lb dogs
12 ct
$4.92 each    $4.92 each
How many 12 cts?
6 ct
$5.19 each    $4.92 each
How many 6 cts?
$5.99 each
   $4.92 each
How many Chewables?
Total Qty: 1 x 1 = 1
Price Per Chewable: $5.99
Subtotal: $5.99
Add to Cart
All items In-Stock and ready for delivery unless otherwise noted
1-25 lb dogs
12 ct
$3.67 each    $3.67 each
How many 12 cts?
6 ct
$3.89 each    $3.67 each
How many 6 cts?
$4.49 each
   $3.67 each
How many Chewables?
Total Qty: 1 x 1 = 1
Price Per Chewable: $4.49
Subtotal: $4.49
Add to Cart
All items In-Stock and ready for delivery unless otherwise noted

View our Tri-Heart Plus video.

What is Tri-Heart Plus?
This monthly oral pet med is used as a combination heartworm preventive and intestinal wormer. Tri-Heart Plus kills the immature form of the heartworm (Dirofilaria immitis), which is transmitted by a mosquito. It is also used for the treatment and control of hookworms (Ancylostoma caninum, A. brasiliense, and Uncinaria stenocephala) and roundworms (ascarids - Toxocara canis, Toxascaris leonina).

Who is it for?
Dogs and puppies over 6 weeks of age. Safe for pregnant/breeding females.

What are the benefits?

Tasty medicine used for both heartworm prevention and intestinal worming
Economical heartworm medication with the same active ingredients as Heartgard Plus
Give year round for complete protection

How does Tri-Heart Plus work?
Tri-Heart Plus is used in the prevention of heartworm infection and the control and treatment of various other worm infections. Tri-Heart Plus contains two active ingredients: ivermectin, which interferes with the parasite's nerve transmission, causing paralysis and death of the immature heartworms (larvae), and Pyrantel pamoate, which also interferes with the parasite's nerve transmission, causing paralysis and death of intestinal worms.

Is there a generic equivalent available?
Yes, both the Tri-Heart Plus and the Iverhart Plus are branded generic alternatives to Heartgard Plus and should be interchangeable as long as the doctor does not indicate "dispense as written".

How is it given?
Tri-Heart Plus must be administered monthly, preferably on the same date each month. Drs. Foster and Smith recommends (and our guarantee requires) that Tri-Heart Plus be given year round, although some veterinarians may recommend giving it only during the mosquito season. If given seasonally, the first dose must be given within 30 days of the dog's first exposure to mosquitoes. The last dose must be given within 30 days after the dog's last exposure to mosquitoes.

Most dogs like the taste of Tri-Heart Plus and will accept the chewable tablet as a treat. The chewable should be administered in a manner that encourages the dog to chew, rather than to swallow without chewing. Tri-Heart Plus Chewables may be broken into pieces and fed to dogs that normally swallow treats whole. Care should be taken that the dog consumes the complete dose, and treated animals should be observed for a few minutes after administration to ensure that part of the dose is not lost or rejected. If not entirely consumed, give another full-recommended dose as soon as possible.

What results can I expect?
Tri-Heart Plus will kill the immature heartworms the dog was exposed to in the preceding month. It will treat an intestinal infection with adult hookworms and roundworms.

What form(s) does it come in?

Please click on "More Information" for possible drug and food interactions with this medication.

More Info

Brand Name
Tri-Heart Plus Chewables

Try Heart Plus

Common Drug Name
Ivermectin plus pyrantel pamoate

What should I discuss with my veterinarian while considering Tri-Heart Plus?
Talk to your veterinarian about the heartworm testing that is recommended before starting your dog on a heartworm prevention program.

Collies or other herding breeds may have a reaction to ivermectin if given over the recommended heartworm prevention dose. If your dog is one of these breeds, and your veterinarian has prescribed Tri-Heart Plus, observe your pet for at least 8 hours after giving the medication for weakness, staggering, dilated pupils, trembling, drooling, or pressing the head against a wall. Contact your veterinarian immediately if you see these signs.

Some intestinal parasites, such as hookworms and roundworms can be spread to people. Talk to your veterinarian about other measures you can take to prevent your pet from being infected with intestinal worms, and protecting yourself.

Notify your veterinarian of any other medications or supplements your dog is taking, and if your dog has had any reactions to previous medications.

What should I do if I miss a dose?
If a dose is missed and over 30 days have gone by since the last dose, give Tri-Heart Plus immediately and resume a monthly dosing schedule. Tell your veterinarian that a dose was missed.

What is the most important information I should know?
If the interval between doses is longer than one month, the efficacy of the drug is reduced.

Who should not take it?
Do not use in puppies less than 6 weeks of age. Considered to be safe to use in pregnant and lactating animals (female animals nursing their young).

Collies and herding breeds may have a reaction to Tri-Heart Plus.

This medication should only be given to the pet for which it was prescribed.

What side effects may be seen when taking Tri-Heart Plus?
Side effects of Tri-Heart Plus are very rare, but may include vomiting and diarrhea. Even more uncommon are incoordination, convulsions, or drooling. Contact your veterinarian if you observe any of these side effects.

How is it stored?
Store between 68°F-77°F (20°C-25°C). Short periods between 59°F-86°F (15°C-30°C) are permitted. Protect product from light. The chewable form of the drug is appealing to pets and children. Store in a secure area to prevent an accidental overdose. Keep out of reach of children and pets.

What should I do if I know of or suspect there has been an overdose?
If you know or suspect your pet has had an overdose, or if you observe diarrhea, vomiting, incoordination, convulsions or drooling, contact your veterinarian immediately.

What should I avoid when giving my pet Tri-Heart Plus?
Although there are no known drug or food interactions with this medication, consult with your veterinarian before using Tri-Heart Plus with any other medications, including vitamins and supplements, since interactions may occur.

Where is more information available?
Ask your veterinarian, consult with one of our pharmacists at 1-800-447-3021, or see the Patient Information Sheet on this medication. For technical assistance or to report suspected adverse reactions, call the manufacturer, Merck, at 1-800-224-5318.

Frequently Asked Questions
Is there a brand name equivalent to Tri-Heart Plus?
Yes. Heartgard Plus is an FDA-approved alternative to Tri-Heart Plus that contains the exact same active ingredients, Ivermectin and Pyrantel, in the exact same amounts as Tri-Heart Plus. Heartgard Plus is beef-flavored.

What is heartworm disease and why is it bad for my dog?
Adult heartworms lay very tiny larvae called microfilariae, which circulate in the blood. They enter a mosquito when it sucks the blood of an infected animal. They mature in the mosquito and then enter the animal's skin when an infected mosquito bites the animal. When the larvae reach about 3 inches, they migrate to the animal's heart where they grow into adults, sometimes reaching a length of 14 inches.

Severely infected dogs can have up to several hundred heartworms in their hearts and vessels. The adult worms can obstruct the different chambers of the heart and the various large blood vessels leading to and from the heart and lungs. In severe infections, other organs, such as the liver, can also be damaged.

Does my dog need a test before I start giving him Tri-Heart Plus?
The American Heartworm Society advises that all adult dogs being started on a heartworm preventative for the first time be tested. After that, periodic, but not necessarily annual re-testing should be performed. The frequency of testing should take into account variables such as:
  • Prevalence of heartworm disease in the area
  • Missed or late doses of heartworm preventative
  • The dog's lifestyle
In areas where the mosquito season in not year-round, puppies born after the mosquito season do not need to be tested. For instance, in Northern Wisconsin, puppies born in January do not need to be tested. Consult with your veterinarian to determine the appropriate testing schedule for your dog.

How often should I give this medication to my dog?.
Tri-Heart Plus is meant to be given every 30 days. When you start your dog on Tri-Heart Plus, make sure to give it to him on the same day every month.

When should I start giving my dog Tri-Heart Plus during the year?
Remember that Tri-Heart Plus kills larvae your dog was exposed to in the preceding 30 days, so if you give your dog a preventative seasonally, give it to him a month after the first mosquito appears.

What if I miss a dose?
If the interval between doses exceeds 30 days, ivermectin's efficacy can be reduced. Therefore, if you miss a dose, give the Tri-Heart Plus as soon as you remember that you missed it. We also recommend that testing the dog for heartworm infection 6-1/2 months after the missed dose.

I have heard that Collies and other herding breeds have trouble with ivermectin. What can you tell me about this?
Collies and related breeds are known to have sensitivity to ivermectin. The dose of ivermectin in a monthly heartworm preventative is relatively low.

When should I start giving my puppy Tri-Heart Plus?
You can start giving Tri-Heart Plus after your puppy reaches 6 weeks of age.

Description of prescription medication Heartgard® Plus and a success story of one dog who has used the medication to prevent heartworm infection.
Heartworm, or Dirofilaria immitus disease is seen in all 50 states. Follow this case from our clinic to see how one dog owner dealt with this devastating disease.
Heartworm infection can be prevented with medications given monthly. This comparison chart describes popular heartworm products, their ingredients, and effectiveness.
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