Major Uses

Lomustine belongs to the nitrosurea class of chemotherapy agents and works by binding DNA to protein or to other DNA strands to prevent it from replicating. It is given to animals to treat cancer. It is used primarily in dogs, but it may also be beneficial in cats. Lomustine is not approved by the Food and Drug Administration for use in animals. However, it is prescribed legally as an extra-label drug by veterinarians.

Lomustine is most commonly used to treat lymphoma (particularly skin lymphoma), brain tumors, mast cell tumors, lung tumors, kidney tumors, and melanoma. Because lomustine is able to penetrate the blood/brain barrier, it can be used to treat cancers of the nervous system that are typically difficult to treat.

Common Precautions

Lomustine is known to cause some potentially serious side effects in animals. It may reduce white blood cell count, and antibiotics are typically given during treatment to help prevent immune system vulnerability. There is also a temporary risk of bleeding associated with use. Other side effects include liver problems, kidney damage, oral inflammation, loss of appetite, hair loss, thinning of the surface of the eye, and scarring of lung tissue. Unlike most other chemotherapy drugs, lomustine does not generally cause upset stomach. However, it does rarely cause diarrhea and vomiting.

Lomustine should not be used in animals that are pregnant, lactating, or to be used for breeding. Animals being treated with lomustine should not be given live vaccinations.

Phenobarbital prevents full effectiveness of lomustine. Additionally, drugs used to suppress bone marrow, such as other chemotherapy medications, chloramphenicol, methimazone, and others, should not be used at the same time as lomustine. Drugs that suppress immune system function, including corticosteroids and other chemotherapy agents, greatly increase the risk of infection when taken along with lomustine.

Lomustine should not be used in animals with a known allergy or hypersensitivity to the drug. Any known or suspected overdose is a medical emergency that requires prompt veterinarian attention.


Lomustine should be kept in a dry, cool location, away from children and pets. This drug should not be stored near heat sources, in damp locations, or in direct sunlight.


Lomustine is available in tablet form and as an injectable, and the drug can be given either orally or intravenously, depending on the animal's chemotherapy protocol.

In dogs, the typical dose of lomustine is 50 to 90 mg/square meter of body surface, administered orally every 21 days. In cats, the typical dose is 60 mg/square meter of body surface, administered orally every 21 days.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

Lomustine should be given on an empty stomach, when possible. Missed doses of lomustine should not be given without first consulting a veterinarian. In most cases, the treatment schedule will require adjustment.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.