HEARTWORM TREATMENT AT HARC

Heartworm Treatment Program

The dog needs to have finished a 30 day course of Doxycycline/Minocycline and have received 2 doses of Ivermectin based heartworm prevention, or Advantage Multi, prior to injections of Melarsomine. Ideally, there should be a 30 day wait period between the Doxycycline and the Melarsomine injections, but there is some flexibility with this wait period.

Two Injection Melarsomine Protocol

This treatment calls for two injections of Melarsomine. The dog will need to have finished the 30 day Doxycycline/Minocycline) treatment and received 2 doses of heartworm prevention. After the injections, the dog is REQUIRED to be on very strict bed rest for 45 days to minimize the possibility of complications. The injections are given 24 hours apart in the clinic under heavy sedation and the dog is monitored thereafter. Most dogs will spend the night at the clinic, but the dog is allowed to go to the foster home if that is more convenient.

The following are the medications required for this form of treatment:

  • Gabapentin (Pain Medication) for 7 days following the injection.

  • Prednisone (Anti-inflammatory) for 28 days following the injections.

  • Doxycycline or Minocycline (Antibiotic) for a full 30 day cycle, PRIOR to the beginning of the injections.

  • Ivermectin based heartworm prevention, 2 consecutive months PRIOR to beginning injections. Advantage Multi is also acceptable.

  • Trazodone is prescribed for some dogs that cannot be kept calm after the injections.

Three Injection Melarsomine Protocol

This treatment calls for three injections of Immiticide/Diroban, and is the recommended treatment protocol by the American Heartworm Society. Similar to the Two Injection Protocol, the dog is required to be on an Ivermectin based heartworm prevention 2 consecutive months PRIOR to receiving any injections. The dog is also required to receive a 30 day cycle of Doxycycline or Minocycline PRIOR to the first injection. Following the 30 day cycle and wait period, the dog will receive his or her first injection of Melarsomine, and will then be REQUIRED to follow strict bed rest for 30 days. Immediately following the 30 day rest period after the first injection, the dog will receive his or her second and third injection of Melarsomine 24 hours apart. The dog will again be required to follow strict bed rest for another 45 days after the two consecutive injections. As with the two injection protocol, the injections are given under heavy sedation. Most dogs will spend the night between the 2 injections at the clinic, but the dog is allowed to go to the foster home if that is more convenient.


Gabapentin (Pain Medication) for 2-3 days following each injection.

Prednisone (Anti-inflammatory) for a full 30 day cycle, following the injections.

Doxycycline or Minocycline (Antibiotic) for a full 30 day cycle, PRIOR to the injections

Ivermectin based heartworm prevention, 2 consecutive months PRIOR to the injections. Advantage Multi is also acceptable.

Trazodone is prescribed for some dogs that cannot be kept calm after the injections.

Home Care - Your Responsibilities

Throughout the recovery period, please watch your pet for coughing, gagging, vomiting, diarrhea, or loss of appetite. Excessive sluggishness, respiratory distress, and coughing up blood are signs of a serious problem that require immediate veterinary attention. The most important thing you can do to minimize complications during treatment is to restrict your pet’s exercise before, during and after the Melarsomine injections. When adult worms die, they collapse and are pushed deeper into the smaller branches of the vessels that supply blood to the lungs. Because exercise increases blood flow to the lungs, it increases the likelihood that dead worms will block blood flow. This can result in severe complications and possibly death. The importance of restricting your dog’s activity cannot be overemphasized.

The dog must be kept on monthly heartworm prevention after heartworm treatment. Dogs can get re-infected with heartworms immediately after heartworm treatment! A heartworm test should be performed 7-9 months after treatment to ensure that all heartworms have died off.


Most rescues opt for the Two Injection Protocol. However, in dogs that are symptomatic (coughing), older or very small, the Three Injection Protocol may be safer and more appropriate. In consultation with the veterinarian, more diagnostics such as chest radiographs and bloodwork may be ordered to assess the optimal plan for the patient.

More information about heartworm disease and heartworm treatment can be found at The Heartworm Society.