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Dr.Fiona, Dog Veterinarian
Category: Dog
Satisfied Customers: 6273
Experience:  16 years experience as a companion animal veterinarian in British Columbia, California and Ontario
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I have several dogs and heartwormer is expensive. I have ...

Customer Question

I have several dogs and heartwormer is expensive. I have heard that it is ok to use equine heartworm medicine on dogs. Is this true? If so, how much would the dosage be ?? All of my dogs are heartworm negative and on monthly prevention.
Submitted: 9 years ago.
Category: Dog
Expert:  Dr.Fiona replied 9 years ago.

Hi there!

Welcome to Just Answer! I would be happy to help you with this question. The short answer to your question is that it is not possible to do this, but let me explain why...

The active ingredient in dog heartworm preventive is ivermectin. You can read more about it here:

As you can see on that website, the dose for dogs is 0.0015 to 0.003 mg per pound (0.003 to 0.006 mg/kg) once a month for heartworm prevention. In a Min Pin, if she weighed 10lbs, this works out to 0.03 - 0.06mg (also written as 30 to 60 micrograms) of ivermectin. In the Nuheart heartworm preventive, the small size contains 68micrograms of Ivermectin per tablet, which is appropriate for a dog of this size.

Here is more about Nuheart products:

The equine product contains 1.87% Ivermectin - which means 18.7mg/mL. Here is more:

Thus, to give just 68 micrograms (or 0.068 MILLIGRAMS) you would have to give your MinPin just 0.036mLs which is less than one drop! It is not possible to accurately dose your little dog with this very concentrated medication intended for horses. You would very likely overdose your small dog, which would be very serious and potentially fatal.

Here is more about it:

So, the short answer to your question is that although these medications contain the same drug, it is not possible to accurately dose a small dog with the equine formula.


If you feel that this has been helpful, please hit the green "Accept" button. I will still be here to provide more information if you need it.


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Customer: replied 9 years ago.
Reply to Dr.Fiona's Post: Dr Fiona,

I failed to mention that several people I know are using this heartwormer (equine) for prevention for their dogs with no ill effects that I can see. I have 3 Min Pins weighing 18-22 lbs, also a medium sized dog 40-45 lbs and 2 large weighing 60-65lbs each, also one weighing 80 lbs. Are you certain that this cannot be safely used to treat my animals? A local vet did sell me some meds for intestinal worms that is equine, I think it is called Anthelban. I want my animals to be protected, but the cost yearly for this medicine alone is a few hundred dollars.Most of these animals are rescues. I need to cut corners, but still be safe.

Expert:  Dr.Fiona replied 9 years ago.

Hey Sandy!

It is just SO hard to draw up a dose with any accuracy for dogs when the product is designed for horses! Let me show you...

Here is the volume of HORSE heartworm medication that you would need to get the same amount of ivermectin as in the Nuheart product for dogs:

Dogs up to 24lbs - 0.0036mL of horse heartworm medication

Dogs 24 - 50lbs - 0.007mL of horse heartworm medication

Dogs 51 - 0.015mL of horse heartworm medication

Now, the smallest syringe I have is an insulin syringe. One gradation on this is 0.01mL. So, you could draw up the dose for the largest dog using this... but not for the Min Pin! If you gave her just half of that it would still be more than 10 times her dose.

Now, I *have* heard of people using the Ivermectin sheep drench (Ivomec Drench for Sheep) as you can see here:

This product is designed for animals more similar in size to a dog than a horse is, so it is not as concentrated, so easier to draw up a more accurate dose for a dog. I cannot recommend doing this, as this is NOT what it is labelled for. But I can tell you the volume of the sheep drench that you would need to give the same amount of Ivermectin as in the NuHeart products. Ivermectin can be given orally.

Dogs up to 24lbs - 0.085 mL of SHEEP heartworm medication

Dogs 24 - 50lbs - 0.17mL of SHEEP heartworm medication

Dogs 51 - 0.34mL of SHEEP heartworm medication

If you were using an insulin syringe to draw this up, the little dog would get the equivalent of "8.5 units" of insulin. A pharmacist could show you where this mark would be on the syringe. The medium dogs would get the equivalent of 17 units, and the large dogs the equivalent of 34units.

Again, I really cannot recommend doing this! However, if you insist on doing it, the Sheep drench is FAR safer than the horse dewormer because it is not as concentrated so there is not so much chance of overdosing them.

I hope this helps! Best wishes! Fiona

Customer: replied 9 years ago.
Thank you!! I can see that these other pets are likely getting too much medicine. It is too much worry, I will continue with the Nuheart. Thank you again!

Expert:  Dr.Fiona replied 9 years ago.


You are so welcome! It really is almost impossible to dose a dog appropriately with the equine product. For your interest (and to pass on to your friends) here is some information about Ivermectin overdose, and symptoms to look for:

Best wishes, Fiona