melarsomine

Melarsomine is an arsenic-containing drug used as an adulticide to treat heartworm disease caused by Dirofilaria immitis in dogs. It is administered as melarsomine dihydrochloride by deep intramuscular injection into the epaxial muscles under veterinary supervision. The medication kills adult heartworms and is typically used after a thorough evaluation of the dog’s health and worm burden.

Before and during treatment, veterinarians commonly employ strategies to reduce inflammatory reactions and complications. Pre-treatment often includes antigen testing, microfilariae testing, and imaging such as chest radiographs or echocardiography to assess organ function and heartworm burden. A course of doxycycline to target Wolbachia bacteria is frequently used to lessen post-treatment inflammation and the risk of thromboembolism. The melarsomine regimen is multi-dose and requires careful scheduling; the injections are given over a short period with strict activity restriction for several weeks after administration to reduce the risk of pulmonary thromboembolism from dieing worms.

Post-treatment monitoring is essential. Dogs are evaluated for adverse effects and response to therapy, and follow-up antigen testing is performed after several months to confirm clearance of infection. Some dogs may require additional monitoring or treatment depending on worm load and clinical status.

Melarsomine is approved for use in dogs and is not routinely used in cats, where heartworm management differs and involves greater risk. Potential adverse effects include coughing, fever, lethargy, loss of appetite, injection-site pain or swelling, and, less commonly, severe inflammatory or hypersensitivity reactions.