Guide to Choosing a Heartworm Treatment Protocol

1

Three-dose (split-dose): melarsomine and doxycycline; activity restriction during protocol and 6–8 weeks after final injection

Kills 99% of heartworms (renders most dogs antigen-negative)

Requires the most veterinary visits of any protocol

Appropriate for all; best approach for all stages of heartworm disease; this is the protocol recommended by AHS

2

Two-dose: melarsomine and doxycycline; activity restriction during protocol and 6–8 weeks after final injection

In studies without doxycycline, this protocol kills 90% of heartworms (clears approximately 75–80% of dogs); doxycycline likely improves the kill

Greater risk for respiratory complications and lower kill compared to 3-dose protocol

Consider in rescue or shelter settings when there are time and/or financial constraints; appropriate for dogs with mild to moderate heartworm disease

3

Nonarsenical adulticide treatment: ivermectin, or moxidectin with doxycycline; activity restriction for months (ideally until antigen-negative)

Approximately 95% of dogs will have "no antigen detected" test result within 1 year

Lung disease progression; time of heartworm death unknown. Risk remains for respiratory complications during nonarsenical protocols.

Appropriate when melarsomine is not available, the dog has had prior life-threatening reaction to melarsomine, or the dog has a comorbidity with a guarded to grave prognosis

4

Slow-kill nonarsenical adulticide treatment with ivermectin, or moxidectin at preventive dosage; activity restriction for months (ideally until antigen-negative)

Likely takes more than 2 years of continuous administration before a "no antigen detected" test result

Risk of selecting for resistant strains of microfilariae; lung disease progression; time of heartworm death unknown. Risk remains for respiratory complications during nonarsenical protocols.

Not recommended; must clear microfilariae; ideally also use an insecticide product to prevent mosquitoes from picking up microfilariae