Your dog has been diagnosed with heartworms, but there are so many different treatments available, you´re having a hard time deciding which one to use. What to do?

Choose the one that fits your budget and your dog´s lifestyle. Some heartworm preventives carry combinations of drugs to control intestinal parasites and fleas, along with heartworms. Dogs that frequent dog parks and often walk in areas where many other dogs walk are more likely to pick up other parasites. Puppies are more prone to have intestinal parasites. People can also be inadvertently infected by intestinal parasites from dogs, so preventives can protect pets and people.

Preventive products should be used year–round, even in areas where mosquitoes only occur seasonally. Heartworm preventives require a prescription due to the possible side effects of administration to a heartworm–positive dog. The daily heartworm preventive contains the active ingredient diethylcarbamazine, which also treats roundworm infections. Caution must be exercised though, when using this treatment, as it can produce severe reactions in your dog. Also, missing two or three days of treatment could result in a lapse of protection.

The monthly heartworm preventives work by killing larvae accumulating in the host during the preceding month. The most commonly used monthly heartworm preventives are shown below:

1. Ivermectin (Heartgard, Iverhart) Given orally. Can be started at 6 weeks of age. Only controls heartworms and has no additional ingredients.

2. Ivermectin + Pyrantel Pamoate (Heartgard Plus, Iverhart Plus, TriHeart Plus) Given orally. Can be started at 6 weeks. Pyrantel controls hookworms and roundworms.

3. Milbemycin oxime (Interceptor) Given orally. Can be started at 4 weeks but pup must weigh 2 lbs. Controls hookworms, roundworms and whipworms.

4. Milbemycin oxime + Lufeneron (Sentinel) Given orally. Can be started at 4 weeks but pup must weigh at least 2 lbs. Controls hookworms, roundworms and whipworms. Lufeneron prevents flea eggs from developing.

5. Selamectin (Revolution) Applied topically on skin. Can be started at 6 weeks. Also controls fleas and ear mites; treats sarcoptic mange and controls the American dog tick.

Once you have assessed your dog´s lifestyle and your preference for oral or topical treatment, and monthly vs. daily, choose the preventive you think will be most appropriate.

Sharon E. Anderson, DVM

Sharon E. Anderson, DVM, answers medically-related questions, but will not attempt to diagnose or recommend specific treatments. Her advice is not meant to replace professional care. If your pet is ill, contact your veterinarian immediately.