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 mo

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 mo, 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

Slow kill with ivermectin, doxycycline

↓ cost, no injections, no hospitalization, shorter treatment duration than slowkill

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

Appropriate only when severe financial or other constraints

5

Slow kill with ivermectin

Inexpensive; no injections

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

Should be avoided

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