Many dog owners may feel tempted to swing by their local farm and feed store and start giving Ivomec to dogs for the purpose of preventing heartworm disease. While it's true that Ivomec contains ivermectin, which is the ingredient found in several popular dog heartworm preventives such as Heartguard or Nuheart, the truth is that giving dogs Ivomec is risky business because dogs need tiny doses and it is very easy to give an overdose and cause ivermectin toxicity in dogs. Veterinarians warn about this risks of giving Ivomec to dogs. While Ivomec can save dog owners a few dollars, mistakes can turn costly, which is why it's best to stick to the safer, easier to dose, prescription FDA approved heartworm preventatives such as Heartgard, Interceptor, and Sentinel.
Using Ivomec For Dogs
Ivomec (1% Ivermectin) is an injectable medication (given through a shot) that is often sold in farm stores and that's labeled for use in cattle and swine. As mentioned, its main active ingredient is ivermectin, the same active ingredient found in heartworm medications for dogs such as Heartguard.
While Ivomec is much cheaper than heartworm medications obtained by the vet, there are several issues that need to be considered before giving it to dogs. One main issue is the fact that this product is specifically labeled for cattle and swine and not for dogs. From a liability perspective, this means that companies producing these products cannot be held liable for veterinary costs associated with its misuse in a different species as in the case of its use in dogs.
Most of all, it must be considered that there are obvious complicating factors when it comes to dosing a much smaller animal than what the product is labeled for. No dosages for dogs will appear on the medication's accompanying leaflet and this often leads to potential guesswork or reliance on unreliable sources of information found throughout the Internet.
"IVOMEC Injection for Cattle and Swine has been developed specifically for use in cattle, swine, reindeer, and American bison only. This product should not be used in other animal species as severe adverse reactions, including fatalities in dogs, may result."~Merial Ivomec Labeling Information
Dosing Problems for Dogs
Dosages of Ivomec in dogs are very small, so much so that dog owners may be required to use what's called a "Tuberculin Syringe" which is a very small syringe that can hold anywhere from one half to one CC ( cubic centimeter of fluid) or they may have to use a special pipette as the one used in labs.
Accuracy of dosing is extremely important considering that even a small amount as a drop can turn out being deadly. Dosing can be close to impossible, especially for the smallest dogs weighing less than 10 pounds.
But how small is a small dosage of Ivomec for dogs? Let's take a look at some math. In cows, Ivomec is injected at a dose of 1ml (milliliter) for 110 lbs. In dogs, the medication is usually given orally (by mouth). Many dogs, being much smaller than cows, will require much smaller dosages, generally in microliters not milliliters, warns veterinarian Dr. Lee.
And another aggravating factor is the fact that some dogs (e.g., collies, Border collies, Australian shepherds, Old English sheepdogs, etc.) may have the MDR1 gene mutation. These dogs can be 10 times more sensitive to ivermectin, so much so that even a milligram could put them into a coma and even cause death, explains veterinarian Dr Rebecca.
If you are really determined to use Ivomec for your dog because of financial constraints or owning several dogs, your best option is to talk frankly with your vet. Chances are, he or she may be willing to work with you. Alternatively, you can consider using generic heartworm medications which can be less costly than the brand types.
"I would strongly recommend against this practice for many reasons. The cattle ivermectin is a very concentrated form and it would d be very easy to give even a little too much. On top of that, it's an off label use of the product, which means it's not designed to be used in such a way...You would have no support from the manufacturer or FDA if you had a problem." ~Dr. Z, veterinarian
Ivermectin Toxicity in Dogs
When dogs are given higher than usual doses of ivermectin, there may be chances for them developing signs of ivermectin toxicity. These dosages though need to be quite high to produce symptoms (exceptions are dogs with the MDR1 gene).
Generally, ivermectin is well tolerated in dogs even at higher doses than the average heartworm pill. Just consider that, dogs who are treated for sarcoptic mange or demodectic mange with ivermectin, are given doses 5 to 6 times higher than that the average heartworm pill, explains veterinarian Dr. Rebecca.
However, with products like Ivomec the chances for overdosing a dog can be quite easy. Signs of ivermectin toxicity in dogs include nausea, vomiting, diarrhea, incoordination, muscle tremors, seizures, dilated pupils, loss of vision, coma and even death, sometimes even with proper veterinary treatment.
Ivomec use in dogs should therefore be used with the utmost caution. There is no antidote for ivermectin toxicity in dogs, only supportive care. If you are planning giving Ivomec to dogs, discuss with your vet and follow dosing directions accordingly. Your vet may give you pre-dosed medication that you can easily administer to your dog.
"Th types of signs that we see with this toxicity tend to be divided into three categories. GI based signs (lethargy, drooling, vomiting, and appetite loss), nervous signs (ie confusion, tremors seizures) and in severe cases, [..] collapse, depression of the heart and breathing rate, blindness and comas." Dr. B. veterinarian
- US Merial: Ivomec Labeling Information