What is Ivermectin Used to Treat in Dogs?
In dogs, Ivermectin is used in the prevention and treatment of various types of internal and external parasites. In fact, in veterinary medicine, Ivermectin is safely used for parasite control in several animal species (dogs, cats, swine, cattle, and horses). Some of Ivermectin uses are approved, and others are extra-label.
Ivermectin for Dog Heartworm Prevention. Ivermectin is the medication of choice for preventing heartworm infestations. It is also used to clear heartworm larvae in dogs with active infection cases. Ivermectin cannot kill adult heartworms living in the heart and pulmonary arteries.
Ivermectin in the Treatment of Worms in Dogs. Ivermectin is efficient in killing and eliminating certain internal parasites like roundworms and hookworms. The medication is also recommended for dogs with capillariasis. However, Ivermectin is not potent against tapeworms.
Ivermectin in the Treatment of External Parasites in Dogs. In higher doses, Ivermectin can be used to treat demodectic mange, sarcoptic mange (scabies), ear mites (notoedric mange), most other mites, and some lice. We must note that Ivermectin is not effective against ticks, fleas, flukes, and flies.
Can I Give My Dog Ivermectin?
Yes, you can give your dog Ivermectin, but only if your veterinarian approves of the use. This is because Ivermectin is generally safe but must not be used in dogs carrying the MDR1 gene. In such dogs, this medication causes irreversible neurotoxicity (CNS damage).
Ivermectin causes damage to the parasite’s central nervous system, which results in paralysis and death (acts like a GABA receptor agonist). The Ivermectin’s toxic effects are not dangerous for mammals because the medication does not cross the blood-brain barrier in most animal species.
However, dogs with MDR1 gene mutation have defective p-glycoprotein transporter, which results in the Ivermectin crossing the barrier and causing toxicity. The p-glycoprotein may also be overwhelmed and become defective in cases of overdose.
Are there any drug interactions I should be aware of?
There are some medications that increase the effects of ivermectin in a pet’s brain (e.g., ketoconazole, itraconazole, cyclosporine, erythromycin, amlodipine besylate, and nifedipine). When high doses of ivermectin are used to treat mite infestations, spinosad (a common flea preventive treatment) should not be administered. Spinosad is safe to use in conjunction with the low doses of ivermectin used in heartworm preventives.
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.
How often can I give my dog ivermectin?
Liquid ivermectin (Ivomec and other brands) is available in 1% injectable solution for treating cattle and pigs, and in 0.08% oral solution for treating sheep (the 0.27% solution has been discontinued). Do not use Ivomec Plus, Ivomec Super, or any other products that contain additional active ingredients.
Note that all of these products are given orally. You should not use pour-on solutions, as they are not safe to give orally. A pour-on solution can be used topically (on the skin, not orally) to treat sarcoptic mange.
In most cases, you will need a syringe (no needle) that measures to the tenth of a cc to administer (see Where to Buy below).
Ivermectin 0.08% solution made for sheep can be used undiluted. An 8 oz (236 ml) bottle of ivermectin 0.08% solution costs around $28, and would be enough to treat 70,000 pounds of dogs.
Ivermectin 1% solution is more readily available, but without diluting it, the amount to give is too small to measure accurately even for large dogs. The proper way to use liquid 1% ivermectin solution for dogs is to dilute the ivermectin with food-grade (USP) glycerin or propylene glycol (liquid ivermectin injectable solutions are made with 40% glycerol and 60% propylene glycol, so we know that ivermectin mixes well with those ingredients). Some people have used vegetable oil instead because it tastes better and is easier to get, but the drug will not mix as well with oil and so the dosage within the solution may not be even. Vegetable oil may work if thoroughly mixed prior to giving and used within a short period; I wouldnt try to store any mixture made with vegetable oil. Note that mixing ivermectin with oil may increase its absorption; this is not a problem for heartworm prevention but might cause problems if giving high doses to control mites or intestinal parasites.
A 50 ml bottle of ivermectin 1% solution costs around $35 and would be enough to treat 150,000 pounds of dogs when fully diluted. There are instructions below for creating a 30:1 dilution, which works best for small dogs and can also be used for large dogs, and also instructions for creating a 9:1 dilution, which is more suited to large dogs. See Buy Ivermectin, Glycerin and Propylene Glycol below for where to find these products.
It is possible to use ivermectin 1% solution undiluted if youre willing to give higher doses than are needed for heartworm prevention. This is safe for most dogs, as long as they do not have the MDR1 mutation that causes sensitivity to ivermectin, and as long as the ivermectin is not combined with spinosad, a flea control ingredient used in Comfortis and Trifexis (also called Vethical AcuGuard and ComboGuard). See Ivermectin Sensitivity below for more information.
An Ivermectin powder product that was mixed with ground corn and designed for pigs appears to have been discontinued.
Keep any unused mixture refrigerated and protected from light. The length of time the diluted mixture will remain potent is unknown. It is safest to mix each batch fresh, just before using. Ivermectin is sensitive to ultraviolet light and should be stored in the dark or by placing containers in an opaque bag. It can be stored at room temperature (no higher than 86 degrees F (30 degrees C)) as long as it is protected from light, heat, and air.
Note that the dosages listed below are the same as is used in Heartgard, but its safe to give a little more. For example, when using Heartgard Green for dogs weighing 26 to 50 pounds, the dosage used is calculated for a 50-pound dog, while a 26-pound dog would get twice as much per pound of body weight. Heartgard Blue is used for dogs weighing up to 25 pounds, so a 5-pound dog would get five times as much per pound of body weight as a 25-pound dog would. Dosages as high as 50 to 100 times the amount used to prevent heartworms are used to treat mites on dogs (demodectic mange).
High dosages of ivermectin are considered safe for all dogs except those with the MDR1 gene mutation that makes them sensitive to ivermectin and other drugs. Commonly affected breeds include the Collie, Australian Shepherd (all sizes), Shetland Sheepdog, English Shepherd, Old English Sheepdog, McNab, Border Collie, German Shepherd, Long-haired Whippet, and Silken Windhound. Mixed-breed dogs can also be affected. There is now a test available to screen for the presence of the mutated MDR1 gene that causes this problem, see Dogs with a Drug Problem for more information.
If your dog is a purebred or mixed-breed from one of the breeds above, or a mixed-breed of unknown parentage, and has not been tested for the MDR1 mutation, be very cautious using high doses of ivermectin for treating demodex, sarcoptic mange, or other parasites. Start with no more than one-third the regular dose for the first few days and monitor your dog closely. Stop the drug immediately if you see any signs of neurologic toxicity, including uncoordination or loss of balance (ataxia), depression, disorientation, excess salivation, pupil dilation, nystagmus (abnormal movement of the eyes), blindness, tremors, recumbency (inability to get up), or coma. Get your dog to a vet for supportive care if signs are severe or prolonged.
Very high doses of ivermectin, such as are used to treat demodex, are also problematic if combined with products that contain spinosad, such as Comfortis and Trifexis (also called Vethical AcuGuard and ComboGuard). Spinosad is a newer flea-control ingredient that increases the risk of neurological side effects from ivermectin. Dogs infected with heartworms may suffer an anaphylactic reaction from the death of too many microfilariae at once when given very high doses of ivermectin as well.
Recent information has come to light that Heartgard may be only 95% effective, rather than 100% effective, in preventing heartworm infections. That means it will destroy 95% of heartworm larvae, not that 95% of dogs receiving Heartgard will remain heartworm-free.
The dosage of ivermectin used in Heartgard was the lowest found to be 100% effective at killing heartworm larvae when the product was originally approved. Since lower doses were less effective, its possible that higher doses may continue to be 100% effective.
Higher doses of ivermectin are safe for all dogs except those with the MDR1 mutation. Dosages as high as 50 times the amount used to prevent heartworms are used to treat mites on dogs (demodectic mange). Very high dosages may also be problematic for dogs infected with Heartworms, and those being treated with Comfortis. See Ivermectin Sensitivity above for more information.
It may be best to double the amount of ivermectin you give your dogs in order to potentially provide better protection from heartworm infection. Again, this does not apply to dogs with the MDR1 mutation.
Note that higher doses of ivermectin are unlikely to be more effective against the resistant strain of heartworms that has been identified in the Mississippi River Valley. See New Information Regarding Heartworm Resistance for details.
I dont endorse the extra-label use of liquid ivermectin for dogs, but Im concerned that people are using it improperly, subjecting their dogs to potentially dangerous levels (for some dogs) of ivermectin. See below for information on how to properly dilute Ivomec (and other ivermectin) 1% solution in order to make it safe to use for dogs. You can use 0.08% sheep drench undiluted.
The dosages shown below are used to duplicate the amount of ivermectin found in Heartgard, and should be given monthly for heartworm prevention.