All heartworm products labeled for dogs in the United States have been tested in dogs with the MDR1 mutation as required by the FDA and have been found to be safe.
Drugs such as ivermectin, selamectin, milbemycin, and moxidectin, are commonly used to treat and prevent parasites like heartworms. At low doses, such as those used in heartworm prevention, these drugs have been shown to be safe even for dogs with the MDR1 mutation. At higher doses, such as those used in treating mange, these drugs can cause neurologic effects in dogs with the MDR1 mutation and should be avoided.
Some of the combination flea and heartworm preventive products (those containing spinosad) should be used cautiously in dogs that are MDR1 mutant/normal because of a risk of serious drug-drug interactions. While a drug may not cause a problem alone, when a combination of two drugs is given together, an adverse reaction can occur.
Testing your dog for the gene mutation is the only way to determine if your dog is at risk.
Our team at WSU has developed a test that can determine if your pet has the MDR1 gene mutation. You can order a test online.