Lomustine (CCNU): veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

CCNU, CeeNU, Gleostine

Species with doses

Dogs and Cats

Routes

PO

Last reviewed

1 October 2026

Indications

• CNS tumours / CNS lymphoma (crosses the blood-brain barrier)
• Relapsed/refractory or first-line (rescue) lymphoma
• Mast cell tumours (high-grade/non-resectable)
• Histiocytic sarcoma; epitheliotropic (cutaneous) T-cell lymphoma

Lomustine (CCNU) dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Lymphoma / MCT / CNS tumour / histiocytic sarcoma (BSA): Dosed by BODY SURFACE AREA. Papich 5e: 70–90 mg/m² every 4 weeks; lymphoma 60 mg/m² every 4 weeks for four treatments; brain tumours 60–80 mg/m² every 6–8 weeks. Plumb’s p.738: 50–90 mg/m² every 2–6 weeks by protocol. CBC before each dose and at the delayed nadir; monitor liver enzymes (irreversible hepatotoxicity reported). Consult an oncologist.

Cats

• Lymphoma / MCT (BSA): Papich 5e: 50–60 mg/m² every 3–6 weeks, or 10–20 mg per cat every 3–6 weeks. Plumb’s p.738: 60 mg/m² every 6 weeks or a single 10 mg dose every 3 weeks. Neutropenia is dose-limiting; nadir at 3–4 weeks in cats.

Contraindications

Pre-existing significant myelosuppression or hepatic disease. Pregnancy (teratogenic/cytotoxic). Known hypersensitivity. Owners unable to handle cytotoxic medication safely. Concurrent hepatotoxins. Reduce/avoid with poor liver function.

Species-specific warnings

Dogs: Cumulative hepatotoxicity is a real, sometimes fatal risk — baseline and pre-dose liver enzymes are mandatory, with hepatoprotectant co-therapy; stop/reduce for rising enzymes.

Adverse effects

• Myelosuppression — neutropenia (nadir can be DELAYED ~1–3 weeks) and CUMULATIVE thrombocytopenia
• HEPATOTOXICITY (cumulative; can be severe/fatal) — monitor liver enzymes
• GI upset (vomiting, diarrhoea, anorexia)
• Pulmonary fibrosis (rare, chronic); renal effects (rare)

Drug interactions

• Other myelosuppressive chemo / radiation: additive marrow suppression
• Hepatotoxic drugs: additive hepatotoxicity (monitor; consider hepatoprotectants)
• Phenobarbital / CYP modulators: may alter activation/metabolism
• Live vaccines: avoid during immunosuppression

Pregnancy and lactation

Contraindicated in pregnancy (teratogenic/cytotoxic). Full cytotoxic handling precautions.

Monitoring

• CBC before each dose AND ~7–14 days later (the nadir is DELAYED) — neutropenia/cumulative thrombocytopenia
• Liver enzymes (ALT etc.) at baseline and before each dose — cumulative hepatotoxicity (stop/adjust if rising)
• Clinical/tumour response; body weight
• Owner cytotoxic-handling precautions (gloves; pregnant persons must not handle)

Toxicity and overdose

Two cumulative, potentially severe toxicities define its use: (1) MYELOSUPPRESSION with a characteristically DELAYED neutrophil nadir (~1–3 weeks) and cumulative thrombocytopenia, and (2) HEPATOTOXICITY that is cumulative and can be fatal (hence baseline/serial liver monitoring and hepatoprotectant co-therapy). GI toxicity and rare pulmonary fibrosis also occur. Overdose intensifies marrow and hepatic injury.

Management: No specific antidote. Discontinue; intensive supportive care for myelosuppression (antibiotics for neutropenic sepsis, ± G-CSF, transfusion) and hepatotoxicity (hepatoprotection with SAMe/silybin/NAC, monitoring). Anticipate the DELAYED nadir — monitor CBC over weeks. Decontaminate large recent ingestions.

Clinical pearls

• The oral, BBB-crossing alkylator — go-to for CNS tumours/CNS lymphoma and a versatile rescue drug for lymphoma, mast cell tumours, histiocytic sarcoma and cutaneous T-cell lymphoma
• Mind the DELAYED myelosuppression: check the CBC before each dose AND ~1–2 weeks later (the nadir comes late and thrombocytopenia is cumulative)
• Monitor the LIVER closely — cumulative hepatotoxicity can be fatal; co-prescribe a hepatoprotectant (SAMe/silybin) and stop for rising enzymes
• Dose by BSA, don't split capsules (use compounding for small patients), and handle with full cytotoxic precautions

Mechanism of action

A nitrosourea alkylating agent that, after metabolic activation, alkylates and CROSS-LINKS DNA (and carbamoylates proteins), preventing replication/transcription and killing dividing cells (cell-cycle non-specific). Its high lipid solubility allows it to cross the blood-brain barrier — the basis of its use in CNS tumours. The same DNA-damaging action on marrow stem cells (with delayed kinetics) and hepatocytes produces its delayed myelosuppression and cumulative hepatotoxicity.

Formulations and products

• 5 / 10 / 40 mg capsule (CeeNU/Gleostine)
• CeeNU / Gleostine — 5 / 10 / 40 mg capsule, Capsule (human-label)

Storage

Capsules: 15–30 °C, dry, protect from light/moisture; handle as a hazardous cytotoxic (gloves), do NOT split/open capsules, dispose appropriately. (Accurate small-patient dosing may require specialist compounding rather than splitting.)

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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Frequently asked questions