Lomustine
1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)
Also known as: CeeNu · Belustine · Cecenu · CiNU · Citosta · Lomeblastin · Lucostine · Prava · CCNU · Gleostine · lomustinum · NSC-79037 · RB1509 · WR-139017
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
This dose is based on body surface area (mg/m²). Convert body weight to body surface area before dosing.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Antineoplastic (CNS neoplasms, lymphomas, mast cell tumors, histiocytic sarcomas) | 50-90 mg/m2 | PO | every 2-6 weeks | — | 🌎 NA |
| All uses (brain tumours, mast cell tumours, lymphoma, histiocytic sarcoma) | 60-80 mg/m2 | PO | q3-4wk | As directed by oncologist | 🌍 EU |
- Antineoplastic (CNS neoplasms, lymphomas, mast cell tumors, histiocytic sarcomas): Dosed in mg/m2, NOT mg/kg. Exact protocol depends on indication.
- All uses (brain tumours, mast cell tumours, lymphoma, histiocytic sarcoma): S-Adenosylmethionine and silybin may be used to prevent or treat hepatotoxicity.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Antineoplastic (CNS neoplasms, lymphomas, mast cell tumors) | 60 mg/m2 | PO | every 6 weeks | — | 🌎 NA |
| Antineoplastic (CNS neoplasms, lymphomas, mast cell tumors) | 10 mg | PO | every 3 weeks | — | 🌎 NA |
| All uses | 30-60 mg/m2 | PO | q4-6wk | As directed by oncologist | 🌍 EU |
- Antineoplastic (CNS neoplasms, lymphomas, mast cell tumors): Administered as a single 10 mg total dose.
- All uses: Dose is suggested but not well established. Specialist advice should be sought, as dosing intervals may need to be increased due to delayed myelosuppression.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Lomustine (commonly known as CCNU) is a highly lipophilic nitrosourea alkylating antineoplastic agent. Because of its high lipid solubility, it readily crosses the blood-brain barrier, making it uniquely valuable for treating central nervous system (CNS) malignancies.
Key Veterinary Indications:
- Mast Cell Tumors (MCTs): Frequently used as a first-line or rescue therapy in dogs and cats.
- Histiocytic Sarcoma: Considered a treatment of choice for localized or disseminated forms in dogs.
- Lymphoma: Often utilized as a rescue agent for relapsing multicentric lymphoma, or as a primary agent for epitheliotropic (cutaneous) lymphoma.
- CNS Neoplasms: Used for primary brain tumors (e.g., gliomas) or metastatic CNS lesions.
Clinical Pearl: Lomustine is notorious for causing delayed, cumulative, and potentially irreversible hepatotoxicity in dogs. Concurrent administration of hepatoprotectants (like SAMe and silymarin) is strongly recommended by many veterinary oncologists.
Mechanism of action
Lomustine is a cell cycle-phase nonspecific antineoplastic drug, meaning it is toxic to cancer cells regardless of their current phase in the division cycle.
- Alkylating Activity: It undergoes spontaneous decomposition in vivo to form reactive intermediates. These intermediates transfer alkyl groups to DNA and RNA → causing cross-linking of DNA strands → preventing DNA replication and RNA transcription.
- Carbamoylation: The drug also causes carbamoylation of cellular proteins (specifically lysine residues) → inhibits DNA repair enzymes, preventing the cancer cell from fixing the alkylation damage, ultimately leading to apoptosis.
Safety & warnings
Contraindications
- Pre-existing severe bone marrow depression
- Active infections
- Pregnancy (Teratogenic - FDA Category D)
- Nursing/lactating animals
- Pre-existing bone marrow suppression
- Pre-existing liver disease
- Pregnancy and lactation
Adverse effects
- Bone marrow depression (anemia, thrombocytopenia, leukopenia) - nadirs typically at 1-6 weeks
- Hepatotoxicity (delayed, cumulative, chronic, and irreversible in dogs)
- Stomatitis
- Alopecia
- Corneal de-epithelization
- Renal toxicity (rare)
- Pulmonary infiltrates or fibrosis (rare)
- Myelosuppression (dose-limiting; severe neutropenia and thrombocytopenia)
- Hepatotoxicity (cumulative, dose-related, potentially irreversible in dogs)
- Gastrointestinal toxicity (vomiting, diarrhea, anorexia)
Precautions
Use only when potential benefits outweigh risks in patients with pre-existing anemia, bone marrow depression, pulmonary function impairment, current infection, impaired renal function, or sensitivity to lomustine. Extreme caution is required in patients who have received previous chemotherapy or radiotherapy due to compromised bone marrow reserves. Hepatotoxicity in dogs can be severe, delayed, and irreversible. Teratogenic in laboratory animals; suppresses gonadal function. Nursing puppies/kittens should receive milk replacer if the mother is treated.
Drug interactions
May increase the risk of severe infection due to additive immunosuppression.
Additive bone marrow depression; concurrent use should be avoided or strictly monitored.
Increased risk of vaccine-induced infection or decreased vaccine efficacy; use with extreme caution or avoid during therapy.
Increased risk of severe and potentially fatal bone marrow suppression.
Altered metabolism of lomustine, which requires hepatic microsomal enzyme hydroxylation. Use with caution.
Enhances the toxicity of lomustine (reported in humans).
Monitoring
- CBC with platelets one week after dosing and prior to next dose (If platelets < 200,000/mcl, stop therapy until thrombocytopenia is resolved)
- Liver function tests (ALT, AST, ALP, Bilirubin) initially before starting treatment and then every 3-4 months
- Complete Blood Count (CBC) including platelets, particularly 7-14 days post-administration (and up to 6 weeks in cats)
- Liver function tests (ALT, AST, ALP, Bilirubin) prior to every dose
- Clinical signs of gastrointestinal toxicity
Pharmacokinetics
Half-life
Absorption
Absorbed rapidly and extensively from the GI tract. Some absorption occurs after topical administration.
Distribution
Lomustine and its active metabolites are widely distributed in the body. Highly lipophilic. While parent lomustine is not detected in the CSF, its active metabolites cross the blood-brain barrier and are detected in substantial concentrations.
Metabolism
Metabolized extensively in the liver to both active and inactive metabolites.
Elimination
Eliminated primarily in the urine.
Overdose
Because of the severe potential toxicity of the drug (profound myelosuppression and hepatotoxicity), overdoses should be treated aggressively.
- Employ gut emptying protocols (emesis, activated charcoal) immediately if exposure was recent and the patient is asymptomatic.
- Provide aggressive supportive care and monitor CBC and liver enzymes closely.
- Consult an animal poison control center or a veterinary oncologist for specific guidance.
Available products
Formulations
- Capsules
- 40 mg oral capsule
Human-labeled
- Lomustine Capsules: 10 mg, 40 mg & 100 mg with mannitol; CeeNu® (Bristol Labs Oncology); (Rx)
- 10 mg capsule
- 40 mg capsule
- 100 mg capsule
Regulatory status
POM (Prescription Only Medicine). Handled under cascade.
POM-V. Handled under the prescribing cascade.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store capsules in well-closed containers at room temperature. Expiration dates of two years are assigned after manufacture.
Client information
Important Safety and Handling Guidelines:
- Cytotoxic Precautions: Lomustine is a chemotherapy drug. Wear disposable gloves when handling the capsules. Do not open, crush, or split the capsules.
- Waste Management: The drug and its toxic metabolites can be detected in the pet's urine and feces for up to 24 hours (some protocols recommend precautions for 48-72 hours) after a dose. Wear gloves when cleaning up urine, feces, or vomit, and wash hands thoroughly afterward. Pregnant women or immunosuppressed individuals should avoid handling the drug or the pet's waste.
When to Contact the Veterinarian:
- Lomustine can cause severe suppression of the bone marrow and liver damage.
- Contact your veterinarian immediately if your pet develops signs of infection, runs a fever, exhibits unusual bruising or bleeding, has yellowing of the whites of the eyes or gums (jaundice), experiences persistent vomiting, diarrhea, or simply becomes lethargic and ill.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.