Melarsomine (melarsomine dihydrochloride) is an organic arsenical chemotherapeutic agent and is a trypanocidal antiparasitic drug. As of 2016 DIROBAN, a generic melarsomine dihydrochloride product, is the only FDA-approved treatment for adult heartworm (Dirofilaria immitis) infection in dogs. It is not approved for treatment in cats, or dogs in late-stage infection. It is marketed by Merial under the trade name Immiticide and is not currently available in the U.S. due to a manufacturing shortage. Sponsored by Anzac Animal Health, LLC and distributed by Zoetis, Inc., DIROBAN is a prescription animal drug supplied as a sterile powder that must be reconstituted with an accompanying sterile water diluent. The exact mode of action on D. immitis is unknown. Post-treatment mortality due to thromboembolism and/or progression of the underlying disease may occur in 10 to 20% of the Class 3 patients treated with DIROBAN.