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Melarsomine for Dogs

By Evan Ware, DVM

Last reviewed: 7/13/2022

Commonly prescribed for: Heartworm

Species: Dogs

Therapeutic Class: Antiparasitic

Basic Information

Melarsomine is an antiparasitic medication derived from an organic arsenic compound that is used in a veterinary hospital setting to treat dogs that are suffering from heartworm disease.

Veterinary Medicine Uses for Melarsomine

Melarsomine contains arsenic, which is the active ingredient that kills both the adult and immature (>4 months old) heartworms. After treatment with melarsomine, the patient should undergo cage rest for four to six weeks. Additional medications that is used to treat heartworm disease include other antiparasitics, antibiotics, and steroids.

Potential Side-Effects of Melarsomine

The most-common side effects of melarsomine include pain, swelling, and tenderness at the injection site; fever, lethargy, a loss of appetite, vomiting, gagging, lung congestion, and depression. Hard nodules also can develop and persist at the injection site. Older dogs, such as those aged eight years or older, tend to be more susceptible to depression, vomiting, and loss of appetite as compared to younger patients.

More-severe side effects of melarsomine, although rare, include coughing up blood, diarrhea, excessive drooling and panting, and death. It is important to note that these signs can be directly related to treating heartworm disease and not necessarily the drug itself.

For this reason, surgical removal of the heartworm may be recommended to help improve the patient's prognosis. If left untreated heartworm disease can prove fatal, so the risks of treatment are usually accepted.

Drug Interactions with Melarsomine

Although melarsomine is FDA-approved for use in canines, there are certain situations where the drug should be avoided or used with extreme caution. For instance, if the pet has a known allergy to melarsomine, it should be avoided. This medication also should be used with extreme caution in patients who are pregnant, nursing, or already receiving treatments for other diseases, especially those affecting the kidneys or lungs.

Melarsomine is approved for use in dogs only. It never should be administered to cats or to other pets.

Melarsomine has been shown to interact with Caparsolate and glucocorticoids, so extra care needs to be practiced in these types of cases.

Precautions for Using Melarsomine

When it is in its powder form, melarsomine should be stored upright at room temperature. Once reconstituted, however, the medicine should be stored in a refrigerator. Melarsomine should be disposed of if not used within 24 hours after reconstitution.
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