By Rania Gollakner, BS, DVM, MPH

What is lomustine?

Lomustine (brand names: Gleostine®, Ceenu®) is an antineoplastic (anticancer) chemotherapy used to treat brain and spinal cord tumors, mast cell tumors, histiocytic sarcomas, or lymphoma.

Its use in cats and dogs to treat certain cancers is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is lomustine given?

Lomustine is given by mouth in the form of a capsule. It may also be compounded into other forms such as chewable tablets and liquid suspensions. Give lomustine with food.

Lomustine is considered a hazardous drug. Do not handle if you are pregnant or nursing. Wear gloves when administering this medication. Measure liquid forms very carefully. On the day your pet receives this medication, and for a few days afterwards, use gloves when handling all bodily waste such as urine, feces, cat litter, blood, or vomit. Throw this waste in a sealable plastic bag, then seal this bag and the gloves in another sealable bag and dispose in the regular garbage.

Pregnant women should not handle this medication.

This medication can take a few weeks before full effects are noted, but side effects can occur immediately. Gradual improvements are usually noticeable after a few days.

What if I miss giving my pet the medication?

If you miss a dose, contact your veterinarian for further instructions, as this medication must be dosed very carefully.

Are there any potential side effects?

Side effects include lack of appetite, vomiting, diarrhea, sores in the mouth, hair loss, or eye ulcers. Serious side effects include bone marrow suppression leading to anemia, decreased platelets, and decreased white blood cells, as well as liver, kidney, or lung damage. Indicators of these effects include bruising, bleeding, fever, severe lethargy, changes in urination, yellowing of the skin or eyes, or shortness of breath.

This moderate-acting medication should stop working in a few days, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Lomustine should not be used in pets that are severely allergic to it. Use this medication with extreme caution in pets with anemia, bone marrow problems, active infections, or liver, kidney, or lung dysfunction; in these cases, this medication should only be used when the potential benefits outweigh the risks. Only use lomustine during pregnancy when the potential benefits to the mother outweigh the risks to the offspring. If use in lactating pets is necessary, use a milk replacer.

Pregnant women should not handle this medication.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with lomustine: myelosuppressive agents and vaccines.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

Liver, kidney, and lung function tests should be performed prior to starting the treatment and immediately prior to the next scheduled dose. Complete blood counts should be performed one week after dosing and immediately prior to the next scheduled dose to evaluate your pet’s fitness to receive that dose. Your veterinarian may monitor your pet to be sure that the medication is working.

How do I store lomustine?

Store this medication in a sealed container at room temperature between 68°F and 77°F (20°C and 25°C). Do not expose this medication to temperatures above 104°F (40°C). Protect from light.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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