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May 2018

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Arsenical Antiparasitic (Systemic Drug)

Prescriber Highlights

  • Organic arsenical adulticide to treat heartworm disease in dogs
  • American Heartworm Society recommends a 3-dose protocol (except for dogs with caval syndrome) after treatment with doxycycline and a macrocyclic lactone
Uses, Indications
  • Four weeks of doxycycline therapy and administration of a macrocyclic lactone is recommended before melarsomine administration
  • Indicated in the treatment of stabilized class I (mild), II (moderate), and III (severe) heartworm disease caused by immature (ie, postlarval, stage L5) to mature adult Dirofilaria immitis infections in dogs
Contraindications, Precautions, Warnings
  • Contraindications

Not recommended for use in cats or patients with class IV (ie, caval syndrome) heartworm disease

  • Precautions

Older dogs may be more susceptible than younger dogs to adverse effects

  • Warnings

Not for IV or SQ use because significant toxicity or tissue damage may occur; large breeds requiring larger volumes may be more susceptible to tissue damage

Side Effects
  • Injection site reactions (eg, pain, swelling, tenderness, reluctance to move) occur in approximately one third of patients 
  • Coughing/gagging, depression, lethargy, anorexia, inappetence, fever, lung congestion, vomiting, and hypersalivation
Drug Interactions
  • Aspirin may complicate therapy; concurrent use is not recommended
  • CNS depressant drugs may cause additive side effects or increase the incidence of the effects
  • Side effects, which include signs of thromboembolism
  • Cardiac biomarkers (eg, troponin I, creatine kinase-MB isoenzyme) may be useful to monitor the effects of worms and adulticide treatment on the heart
  • Test for microfilaria 30 days after the last melarsomine dose
  • Perform an antigen test 6 months after the last melarsomine dose
Client Information
  • Strict exercise restriction after dosing is essential
  • Because of the seriousness of the disease and the potential for morbidity and mortality associated with treatment, clients should give their informed consent before treatment begins
Dosage Forms
  • The following product is labeled for veterinary use:
    • Melarsomine dihydrochloride powder for injection: 50 mg/vial

Compiled and summarized from Plumb’s® Veterinary Drugs by Shannon Palermo, VMD

Information about this drug was adapted from Plumb’s® Veterinary Drugs. Further details and more therapeutics can be found with a subscription at

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