Major Uses

Melarsomine is an arsenic-based drug that treats heartworm infections in animals by killing adult heartworms living in the arteries of the lungs. Melarsomine does not have any effect on heartworm microfilaria. Use of this drug will not cause arsenic poisoning.

Melarsomine is for use in dogs only. It should not ever be used in cats. It is for treatment of asymptomatic or mild heartworm disease and should not be used to treat severe heartworm disease.

Common Precautions

Side effects associated with use of melarsomine include swelling, pain, and reluctance to move. It may also cause skin and muscle irritation at the injection site. Fever, vomiting, lethargy, coughing, and lack of appetite are other possible side effects associated with use. These symptoms may be caused by the death of adult heartworms inside the body. Supportive treatment with prednisone may help.

Melarsomine should not be used to treat severe heartworm disease. Rapidly killing large numbers of heartworms can lead to a potentially-fatal syndrome. Dogs should undergo treatment to stabilize heartworm disease prior to treatment with melarsomine. It is not known if melarsomine is safe for use in breeding, lactating, or pregnant animals.

Melarsomine should not be used in animals with a known allergy or hypersensitivity to the drug. Overdose of melarsomine is possible and may be very serious. Care must be taken when dosing and administering this drug. Overdose symptoms vary, but may include panting, restlessness, vomiting, excessive salivation, and fever. Any known or suspected overdose should be considered a medical emergency and should be reported to a veterinarian right away.


Melarsomine should be store upright and at room temperature. Following reconstitution, the solution should be stored in the refrigerator and in the original packaging. This drug should be kept away from light and out of the reach of children and animals.


Melarsomine is available in 50 mg per vial bottles for injection.

The typical dose of melarsomine is 1 mg/lb (2.2 mg/kg) deep within the epiaxial muscles over the spine. Dosing is twice within 24 hours. In cases of advanced heartworm disease, a single dose should be administered within 24 hours, followed by a period of one month or more. Then, a second and third dose may be administered as usual. Correct calculations when dosing melarsomine are crucial. This drug should only be administered into the muscle tissue. It should never be injected into a vein or just under the skin.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.