Side Effects and Risks of Ivermectin in Dogs
Common Side Effects
Ivermectin is a safe and effective medication that prevents a variety of parasitic infections in dogs, including heartworm infections. Even when administered correctly, ivermectin can sometimes cause mild side effects in dogs. These effects vary from dog to dog, depending on their sensitivity, dosage, and overall health. Most commonly, dog owners might observe symptoms like mild diarrhea, drooling, or vomiting. These effects often resolve on their own and don’t require intervention. In some cases, your dog might seem a bit off, maybe acting more tired than usual or not as interested in food. These signs should still be reported to your vet, especially if they persist or worsen.
One often overlooked effect is disorientation or a slight wobble in movement. While not as dangerous as other symptoms, these signs can signal that your dog’s body is reacting poorly to the drug. Think of it like a mild hangover: they’ll bounce back, but you need to monitor them closely. Always observe your dog closely after administration and jot down any strange behaviors. That way, if you ever need to talk to your vet, you’ll have solid info ready.
Severe Adverse Reactions
Now, let’s get into the more serious stuff. While rare, ivermectin toxicity can happen—especially in breeds that are genetically sensitive or if a dog accidentally ingests a high dose. Severe side effects may include:
- Loss of coordination (ataxia)
- Tremors or seizures
- Coma
- Dilated pupils or blindness
- Respiratory distress
These symptoms are no joke. If your dog starts twitching, drooling excessively, or collapses, you need to call your vet immediately or rush them to an emergency clinic. The good news? These reactions are uncommon when the drug is used responsibly and under veterinary supervision. But accidents happen—like a curious pup chewing through a box of horse ivermectin—so you have to keep medications safely stored.
Interactions with Other Medications
Let’s not forget drug interactions. Ivermectin can interact with other medications, which could enhance its effects or cause unexpected reactions. Drugs like ketoconazole, cyclosporine, and certain sedatives can interfere with ivermectin’s processing in the liver. This could mean the ivermectin stays in your dog’s system longer and in higher concentrations, raising the risk of side effects.
Also, if your dog is on any neurological medications, such as those for seizures or anxiety, you must let your vet know. The combo might not be dangerous, but why take the risk? The vet might suggest an alternative dewormer or tweak your dog’s current meds to make ivermectin safer to use.
Ivermectin Alternatives for Dogs
Natural Alternatives to Ivermectin
If you’re not comfortable using ivermectin or your dog is one of those breeds sensitive to it, don’t worry—you’ve got options. Some pet parents swear by natural or holistic remedies. These include ingredients like diatomaceous earth, garlic (in safe amounts), neem oil, and even apple cider vinegar. While these aren’t as potent as ivermectin, they can help keep parasites at bay when used consistently.
Diatomaceous earth, for example, can be sprinkled on your dog’s bedding or used as a supplement to kill internal parasites. Neem oil is great for skin mites and can also repel fleas. But here’s the catch—natural doesn’t always mean safe. Always consult a holistic vet before trying out these alternatives, especially if your dog is already on medications or has a health condition.
Prescription-Based Alternatives
If you want to stay in the vet-approved lane but avoid ivermectin, there are other prescription treatments available. These include:
- Milbemycin oxime (found in Sentinel, Interceptor)
- Selamectin (Revolution)
- Moxidectin (Advantage Multi, ProHeart)
- Spinosad-based products (Comfortis)
Each of these has its pros and cons. For instance, Milbemycin is effective for heartworm prevention and some intestinal worms, and it’s often safer for breeds with the MDR1 mutation. Selamectin is applied topically and can treat fleas and mites. Your vet can help you choose based on your dog’s age, weight, breed, and overall health.
Over-the-Counter Alternatives
There are also OTC parasite preventatives available at pet stores and online. While many of these are lower in strength compared to prescription medications, some dog owners prefer them for light, routine deworming. However, they aren’t as rigorously tested, and you won’t get the same level of protection against serious issues like heartworm.
Look for products containing ingredients like pyrantel pamoate, fenbendazole, or praziquantel. These can handle roundworms, hookworms, and tapeworms, respectively. Again, consult your vet—even OTC products can have side effects or interactions.
Breeds That Should Avoid Ivermectin
Collies and Related Breeds
Certain dog breeds are genetically predisposed to ivermectin sensitivity. The most well-known among these are Collies, but the risk also extends to:
- Border Collies
- Australian Shepherds
- Shetland Sheepdogs (Shelties)
- Old English Sheepdogs
- Longhaired Whippets
Why? These breeds often carry a mutation in the MDR1 gene, which stands for “multi-drug resistance gene.” When ivermectin crosses into the brain in dogs with this mutation, it can cause neurotoxicity—even at doses safe for other breeds. That’s why these breeds should be either tested for the MDR1 mutation or completely avoid ivermectin-based treatments unless specifically cleared by a vet.
How to Know If Your Dog Has the MDR1 Gene
There’s a simple cheek-swab test that vets and laboratories use to check if your dog carries the MDR1 gene. This genetic test is quick, affordable, and it could literally save your dog’s life. Once you know your dog’s status, you and your vet can make more informed decisions on parasite control and even other medications like chemo drugs, which are also impacted by this gene.
Breeders and rescue organizations should ideally provide this genetic information before adoption or sale, especially if you’re adopting one of the high-risk breeds. If they don’t, it’s worth doing the test yourself—it’s a one-time check that could have lifelong benefits.
Administration Tips for Dog Owners
Giving Ivermectin Orally
Oral ivermectin is the most common form used for dogs, usually in tablet or liquid form. Tablets are often flavored to make them more palatable—think beef or chicken. For finicky dogs, wrapping the tablet in cheese or a bit of peanut butter can work wonders. Liquid ivermectin can be mixed into food, but you’ll need a precise syringe to measure the correct dose.
Always follow your vet’s instructions and measure accurately. Even a tiny overdose can be dangerous. Use a syringe or dropper marked with clear increments and never estimate “by eye.”
Using Topical Ivermectin
Some forms of ivermectin are applied directly to the skin—often used for treating mites or lice infestations. These are especially useful for dogs who hate taking pills. The medication is typically applied between the shoulder blades where the dog can’t lick it off. After application, make sure your dog doesn’t roll around or get wet for at least 24 hours.
Also, keep your hands clean—use gloves during application and wash up afterward. Keep other pets and children away until the medication dries.
What to Do in Case of Overdose
Accidents happen. Maybe your dog chewed through a pill bottle, or you gave a second dose by mistake. First step: don’t panic. Second step: call your vet or the nearest emergency animal clinic immediately. Symptoms of overdose include:
- Muscle tremors
- Disorientation
- Excessive salivation
- Blindness
- Coma
Activated charcoal may be given to limit absorption, but only a vet can advise on that. The sooner you act, the better the outcome.
