Side Effects of Ivermectin in Canines

Ivermectin is a monthly heartworm medication for dogs that can also be used to treat ear mites. While Ivermectin is generally well tolerated by most dogs, there are breeds that are particularly sensitive to the drug. Dog owners should carefully monitor their pets for adverse side effects.

  1. Ivermectin Toxicity

    • Toxicity occurs when 10 to 20 times the recommended dose of Ivermectin is administered to dogs. Certain breeds, such as the Australian shepherd, Shetland sheepdog, Old English sheepdog, English sheepdog and collies, have what's known as "breed sensitivity" to Ivermectin, which means that toxicity can occur at what would be a normal dosing level for other breeds. Ivermectin may still be used on dogs with breed sensitivity but the dogs should be monitored closely for signs of overdose such as disorientation, blindness, stumbling or tremors.

    Nervous System Damage

    • In breeds that have a genetic predisposition to Ivermectin sensitivity (as mentioned above), the drug may cause nervous-system side effects. These include muscle weakness lethargy, and seizures which may appear at normal doses. A genetic test (cotton swab by mouth) is administered to dogs believed to carry the genetic marker for Ivermectin sensitivity or an extremely low dose of the drug is administered to see if the dog will develop side effects.

    Digestion and Depression

    • As Ivermectin is processed through the dog's body, it may cause excess salivation and diarrhea, which will lead to a lack of appetite. Breeds across the board have shown to experience symptoms of depression when using Ivermectin as well, which may be a factor of its nervous-system involvement though no formal study has been conducted to confirm this.