Melarsomine
Also known as: Immiticide, Diroban
> **CRITICAL WARNING: STRICT CAGE REST IS MANDATORY.** * **Exercise Restriction**: As the adult heartworms die, they break apart and are carried into the lungs. Any increase in heart rate (from walking, playing, or excitement) forces these worm fragments deeper into the small blood vessels of the lungs, causing a potentially fatal blockage (pulmonary thromboembolism). Your dog must be kept strictly confined to a cage or small room for several weeks after treatment. * **Injection Site Pain**: The medication is given via a deep injection into the back muscles. It is normal for your dog to be sore, reluctant to move, or have a small lump at the injection site. * **What to Watch For**: Monitor your dog closely for coughing, gagging, fever, lethargy, or loss of appetite. * **Emergency Signs**: If your dog experiences severe difficulty breathing, pale or blue gums, or collapses, seek emergency veterinary care immediately.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Heartworm disease (Class I & II)
- Heartworm disease (Class III)
- Heartworm disease (Alternative Protocol / AHS Treatment of Choice)
How it is given
Possible side effects
- Injection site reactions (pain, swelling, tenderness, firm nodules)
- Coughing/gagging
- Depression/lethargy
- Anorexia/inappetence
- Excessive salivation
- Fever
- Lung congestion
- Vomiting
- Pulmonary thromboembolism (can be fatal)
- Paresis and paralysis (rare)
Cautions & contraindications
- Class IV (very severe) heartworm disease / Caval syndrome
- Cats (reportedly very toxic)
- Intravenous (IV) administration
- Subcutaneous (SC) administration
- Low margin of safety; calculate dosages very carefully (do not confuse mg/lb with mg/kg). Administer ONLY via deep IM injection in the lumbar epaxial muscles (L3-L5). Do NOT give IV or SC, as significant toxicity or tissue necrosis may occur. Strict cage rest (2-4 weeks) is mandatory to prevent fatal pulmonary thromboembolism. Older dogs (>8 years) and those with severe pulmonary artery disease are at higher risk for adverse effects. Avoid human exposure; wash hands after use or wear gloves. If human exposure occurs, contact a physician.
Drug interactions
- Aspirin: Has been shown not to reduce adverse effects and may complicate therapy; use is not recommended.
- CNS Depressant Drugs: Drugs that have similar adverse effects (e.g., depression) may cause additive adverse effects or increase their incidence when used with melarsomine.
Frequently asked questions
What is Melarsomine used for in pets?
> **CRITICAL WARNING: STRICT CAGE REST IS MANDATORY.** * **Exercise Restriction**: As the adult heartworms die, they break apart and are carried into the lungs. Any increase in heart rate (from walking, playing, or excitement) forces these worm fragments deeper into the small blood vessels of the lungs, causing a potentially fatal blockage (pulmonary thromboembolism). Your dog must be kept strictly confined to a cage or small room for several weeks after treatment. * **Injection Site Pain**: The medication is given via a deep injection into the back muscles. It is normal for your dog to be sore, reluctant to move, or have a small lump at the injection site. * **What to Watch For**: Monitor your dog closely for coughing, gagging, fever, lethargy, or loss of appetite. * **Emergency Signs**: If your dog experiences severe difficulty breathing, pale or blue gums, or collapses, seek emergency veterinary care immediately.
Is Melarsomine safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
Worried about your pet?
Peqaboo’s AI helps you track symptoms, understand lab reports, and know when to see a vet.
Get the Peqaboo app