Melarsomine (Immiticide®) for Dogs

Overview of Melarsomine for Dogs

Melarsomine, also known by the brand name Immiticide®, is an injectable drug used to treat heartworm infection for dogs. It is often used in a 3 dose protocol and often used after treatment with doxycycline or minocycline. Melarsomine is NOT recommended for use in cats.
Canine heartworm disease is an important and all too common problem. While there are excellent and safe methods for preventing infection, regrettably, dogs still become infected. Heartworm infection is treated in several ways.
One part of treatment involves killing the adult parasite (adulticidal therapy).
Another part of treatment is killing any microscopic offspring (microfilaria) in the blood.
Finally, preventing further infection with a heartworm preventative is important.
Melarsomine is the drug of choice for the first stage and is effective for killing adult heartworms living in the arteries of the lungs.
Melarsomine is an arsenic-based drug. Although these drugs are known to kill adult heartworms, the exact method of the killing action is unknown.
Melarsomine administration does not result in arsenic poisoning.
Melarsomine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.

Melarsomine is used to treat heartworm infection in dogs. The precise method used (one or two stage) depends on the severity of the disease and the need for supportive care.
Melarsomine can only treat adult heartworms and has no effect on microfilaria.

While generally safe and effective when prescribed by a veterinarian, melarsomine can cause side effects in some animals.
Melarsomine should not be used in animals with known hypersensitivity or allergy to the drug.
Melarsomine should never be used in cats.
Care must be taken to avoid melarsomine administration in severe heartworm disease. Rapid kill of large amount of heartworms can lead to a serious and fatal syndrome.
Melarsomine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with melarsomine.
Some adverse effects of melarsomine include skin and muscle irritation at the injection site, pain, swelling and reluctance to move.
Coughing, lethargy, lack of appetite, fever and vomiting have also been reported. Many of these symptoms are likely related to the killing of adult heartworms. As the worms die they obstruct arteries of the lung and create a lung tissue reaction. This situation often requires supportive treatment with the steroid drug prednisone.
There is a low margin of safety with melarsomine; overdose complications can occur if an incorrect dose is given.

Medication should never be administered without first consulting your veterinarian.
The dose of melarsomine is crucial. Correct calculations are imperative. The exact injection technique recommended by the manufacturer should be used.
Melarsomine is to be given by intramuscular injection only. It should never be given just under the skin or into a vein.
Many dogs require treatments to stabilize the disease prior to administration of melarsomine. This may include prednisone (steroid) treatment to control lung inflammation or treatments for heart failure.
The usual dose is 1 mg per pound (2.2 mg/kg) deep within the muscles over the spine (epiaxial muscles). This dose should be given twice within 24 hours.
In advanced cases of heartworm disease, a two-stage treatment is safer. Initially only one dose is given. At least one month later, a two-dose treatment is given.
Repeated doses are based on the severity of the heartworm disease and response to treatment.
Strict cage rest is recommended after Melarsomine treatment.