Merck Manual

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Guide to Choosing Heartworm Therapeutic Protocol

Guide to Choosing Heartworm Therapeutic Protocol

Protocol

Advantages

Disadvantages

Utilitya

1

Split dose (3 injections), melarsomine and doxycycline; thoracic radiographs, CBC, UA, chemistry panel, coagulation profile

↑ efficacy, ↓ risk of PTE, safety of phased worm kill, no resistance concern

Cost $$$$; exercise restriction for 2 months

Appropriate for all; best approach for severe HW disease

2

Standard dose (2 injections), melarsomine and doxycycline; thoracic radiographs, CBC, UA, chemistry panel, coagulation profile

↓ cost, ↓ risk of PTE (vs standard dose), exercise restriction only 1 month, no resistance concern

Cost $$$; ↑ risk of PTE (vs split dose); ↓ kill efficacy (vs split dose)

Appropriate when financial constraints and mild to moderate HW disease

3

Standard dose (2 injections), melarsomine

↓ cost; exercise restriction only 1 mo, no resistance concern, easier for shelters

Cost $$; ↑ risk of PTE (vs standard dose); ↓ kill efficacy (vs split dose); cage rest imperative

Appropriate when financial constraints and mild HW disease

4

Non-arsenical adulticidal therapy: oral ivermectin, topical moxidectin/imidacloprid, or oral moxidectin, at preventive dosage, with doxycycline

↓ cost, no injections, no hospitalization, shorter treatment duration than slow kill protocol

Cost $; ↑ risk of resistance, not approved by AHS, ~12-month course, lung disease progression, time of HW death unknown

Appropriate when there are severe financial or other constraints, lack of melarsomine availability, or failure of melarsomine treatment to clear dog previously

5

Slow kill non-arsenical adulticidal therapy with ivermectin, topical moxidectin/imidacloprid, or oral moxidectin, at preventive dosage

Inexpensive; no injections

↑ risk of resistance, 30-month course, lung disease progression, time of HW death unknown

Should be avoided; MUST clear microfilariae

a None of these is appropriate for initial management of caval syndrome but may be used to complete therapy after worm removal.

UA = urinalysis; PTE = pulmonary thromboembolism; AHS = American Heartworm Society; $ = relative cost