A compressed two-dose melarsomine protocol may help animal shelters expand access to heartworm treatment by reducing the time, cost, and resources required, according to a randomized clinical trial published in the Journal of the American Veterinary Medical Association (JAVMA).

The study compared the safety and efficacy of two-dose and standard three-dose melarsomine protocols in 168 dogs with Class 1 or 2 heartworm disease. Conducted from April 2024 to December 2025, the trial evaluated both approaches alongside doxycycline, moxidectin, and prednisone.

Dogs receiving the two-dose protocol received melarsomine injections on consecutive days 14 and 15, while the three-dose group received injections on days 14, 44, and 45. Both groups underwent exercise restriction for four weeks following treatment.

The two-dose protocol reportedly achieved 95.3 per cent efficacy, compared with 98.8 per cent for the three-dose approach. All dogs survived treatment, and complications were uncommon. Seven dogs required thoracic radiographs, with or without additional treatment, but none required intensive management.

The findings could have important implications for shelters managing overcrowding and limited budgets. Shortening the treatment timeline and reducing resource demands may allow facilities to treat more heartworm-positive dogs, improve adoption opportunities, and reserve resources for other animals in need.

The research involved Lucky Dog Animal Rescue, the University of Florida Shelter Medicine Program, Toronto Humane Society, and PetSmart Charities.

The authors concluded that the compressed two-dose protocol, when combined with doxycycline, moxidectin and prednisone, was safe and effective.