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Safety Tips for Using Heartworm Preventive Medications on Dogs

Proper Application of Dog Heartworm Prevention Medication

By Jennifer Kvamme, DVM

Ensuring our dogs remain heartworm-free is not only cost-effective but also significantly simpler and safer than managing a full-blown disease. However, it is crucial to administer heartworm preventives correctly, prioritizing both your safety and your dog’s well-being.

Consult Your Veterinarian First

Before administering any heartworm medication to your dog, it is imperative to consult your veterinarian. Only approved heartworm medications should be used, and they must be given in the appropriate dosage based on your dog’s age, weight, and health condition. Your veterinarian will require a negative heartworm test before prescribing the medication. Therefore, it is essential to have your dog tested for heartworms beforehand. Your veterinarian will only issue a prescription for a heartworm preventive if your dog tests negative for heartworms.

Various types of heartworm preventive medications are commonly used today, many of which offer multiple benefits. Some preventives not only control heartworms but also target intestinal and external parasites.

Oral Heartworm Medications

Ivermectin and milbemycin are common active ingredients found in today’s heartworm preventives. Ivermectin, which has been utilized for decades to prevent heartworm disease in dogs, typically causes few side effects when administered at the correct dosage. However, some dogs may exhibit vomiting, diarrhea, or incoordination. In cases of allergic reactions to heartworm medication, dogs may experience itching, hives, facial swelling, or even seizures or shock.

Certain breeds, such as Collies, Sheepdogs, Australian Shepherds, and Whippets, are predisposed to react adversely to ivermectin and milbemycin due to a genetic mutation. This mutation impedes their ability to metabolize the heartworm medication properly, leading to seizures and potentially fatal outcomes. If your dog belongs to one of these breeds, your veterinarian can recommend alternative heartworm preventives. For added assurance, you can request a DNA test from your veterinarian to determine whether your dog carries the genetic mutation.

Topical Heartworm Medications

Newer topical or spot-on medications offer protection not only against heartworms but also fleas, ticks, mites, and other parasites. Depending on the chosen brand, your dog can benefit from comprehensive protection against various internal and external parasites with just one monthly application. Selamectin and moxidectin function by being absorbed into the dog’s skin and accumulating in the oil glands beneath the skin, gradually releasing the drug over time to safeguard the dog.

When administering these types of heartworm medications, it’s important to avoid contact with your skin or eyes. Separate the fur between the shoulder blades to expose the skin beneath and apply the liquid directly onto the skin, not the fur. After handling these medications, wash your hands thoroughly or wear disposable gloves to prevent skin contact. Always adhere to the instructions on the label meticulously. Keep your dog indoors and supervise them for approximately 30 minutes after application. Ensure that children and other animals are kept away while the heartworm medication is being absorbed.

Although adverse reactions to these preventives are rare, they can occur. Potential side effects may include vomiting, diarrhea, drooling, panting, and trembling. Some dogs may experience allergic reactions similar to those observed with ivermectin. Additionally, hair loss at the application site has been reported.

Injectable Heartworm Preventive

An injectable moxidectin product, first approved for canine use in 2001, provides six months of heartworm prevention and eradicates hookworms with a single injection. After a voluntary recall in 2004, it was reintroduced in 2008 under a risk management program in coordination with the U.S. Food and Drug Administration. Veterinarians offering this product must be registered with the manufacturer and undergo training before purchasing it.

Only licensed veterinarians are authorized to administer this product, following comprehensive disclosure of its risks and side effects to pet owners. Owners are required to sign a consent form, and veterinarians must maintain records of each product’s lot number in case of reported side effects. Adverse effects may include facial swelling, itching, vomiting, diarrhea, seizures, or shock.

Other Heartworm Medication Safety Tips

Consider these essential tips when administering heartworm preventives to your dog:

  • Consult your veterinarian to determine the appropriate dosage and type of heartworm medication for your dog before administration.
  • Thoroughly read all labels before using any medication.
  • Store products out of reach of children and pets, such as in a locked cabinet.
  • Monitor your dog for any potential side effects and promptly contact your veterinarian to report any issues.
  • Avoid giving your dog more than one type of heartworm preventive medication simultaneously.
  • Inquire with your veterinarian about the necessity of year-round heartworm preventive treatment, particularly in regions with warmer climates where mosquitoes are prevalent.
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