Chlorambucil: veterinary dose and monograph

At a glance

Drug class

Veterinary drug

Also known as

Leukeran, Chlorambucil

Species with doses

Dogs and Cats

Routes

PO

Last reviewed

1 October 2026

Indications

• Feline chronic enteropathy / inflammatory bowel disease (with prednisolone)
• Feline small-cell (low-grade) alimentary lymphoma (with prednisolone)
• Immune-mediated diseases needing a steroid-sparing immunosuppressant (esp. cats)
• Indolent lymphoid neoplasia / chronic lymphocytic leukaemia (dogs and cats)

Chlorambucil 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

• Indolent lymphoid neoplasia / chronic enteropathy: Papich 5e: 4 mg/m² q24h then q48h (≈0.1–0.2 mg/kg); intestinal disease 4–6 mg/m² q24h for 7–21 days then reduce. Plumb’s p.249: lymphoproliferative disease/macroglobulinaemia 2–4 mg/m² q24–48h (Gilson & Page); lymphoma with prednisone 6–8 mg/m² every other day (Ogilvie); IBD 1.5 mg/m² every other day (Marks). CBC every 2–3 weeks.
• Immune-mediated disease (pemphigus, glomerulonephritis): Plumb’s p.249: glomerulonephritis 0.1–0.2 mg/kg PO daily or every other day (Vaden & Grauer); pemphigus 0.1–0.2 mg/kg daily with corticosteroids until marked improvement (4–8 weeks), then alternate days and taper (White). Monitor CBC.

Cats

• IBD / small-cell alimentary lymphoma (with prednisolone): Papich 5e: IBD 2 mg/cat q48–72h; cancer 2 mg/cat q48h. Plumb’s p.249: cats >4 kg 2 mg q48h for 2–4 weeks then taper to q72–96h, cats <4 kg start q72h (Moore); 15 mg/m² daily for 4 days repeated every 3 weeks with prednisolone, or 2 mg every 4 days indefinitely (Marks); cats <2 kg 2 mg weekly (Gruffyd-Jones). Do not split tablets; monitor CBC.
• Immune-mediated disease (IMHA, pemphigus, dermatoses): Papich 5e: 0.1–0.2 mg/kg (about ½ tablet) q24h then q48h, usually with corticosteroids; IMHA 2 mg/cat q48h. Plumb’s p.249: pemphigus foliaceus 0.1–0.2 mg/kg q24–48h (Hillier); 2 mg/cat q48h (Ashley). Slow onset; myelosuppression — monitor CBC.

Contraindications

Significant pre-existing myelosuppression. Pregnancy (teratogenic/cytotoxic). Known hypersensitivity. Severe hepatic/renal impairment (caution). Handle with cytotoxic precautions; pregnant individuals should not handle. Do not crush/split tablets.

Species-specific warnings

Cats: High-dose chlorambucil can rarely cause a reversible neurotoxic myoclonus in cats — use established protocols and monitor; the usual issue is mild gradual myelosuppression (check CBC).

Adverse effects

• Myelosuppression — usually mild, gradual (neutropenia, thrombocytopenia)
• GI upset (vomiting, anorexia)
• Rare: hepatotoxicity, neurotoxicity (high-dose, e.g. myoclonus in cats)
• Alopecia/whisker changes (occasional)

Drug interactions

• Other myelosuppressive drugs: additive marrow suppression
• Live vaccines: avoid during immunosuppression
• Usually combined with corticosteroids (synergistic immunosuppression/anti-tumour)
• No major CYP interactions of routine note

Pregnancy and lactation

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

Monitoring

• CBC every ~1–2 weeks initially, then periodically (myelosuppression can be gradual/delayed)
• Clinical/disease response (GI signs, body weight in IBD/lymphoma; haematology in CLL)
• Liver values periodically
• Owner handling precautions (gloves; pregnant persons must not handle)

Toxicity and overdose

Generally mild and gradual — the dose-limiting toxicity is myelosuppression (slowly developing neutropenia/thrombocytopenia), with GI upset and occasional hepatotoxicity. High-dose exposure can rarely cause neurotoxicity (e.g. reversible myoclonus in cats). No haemorrhagic cystitis (unlike cyclophosphamide). Overdose intensifies marrow suppression.

Management: No specific antidote. Discontinue; supportive care for myelosuppression (antibiotics for neutropenic sepsis, ± G-CSF, transfusion if needed) and GI signs. Monitor CBC closely (nadir may be delayed). Decontaminate large recent ingestions.

Clinical pearls

• The CAT-SAFE alkylator/immunosuppressant — the workhorse (with prednisolone) for feline IBD and small-cell alimentary lymphoma, and the alternative to azathioprine (which is contraindicated in cats)
• Gentle and gradual — predictable mild myelosuppression and, unlike cyclophosphamide, NO haemorrhagic cystitis
• Know your protocol: daily, every-other-day, or pulse (e.g. 4 days every 3 weeks) — and always pair with a corticosteroid
• Monitor the CBC, refrigerate the tablets, handle with gloves and never split the 2 mg tablets (cytotoxic)

Mechanism of action

A nitrogen-mustard alkylating agent that cross-links DNA, impairing replication and transcription in rapidly dividing cells — preferentially suppressing lymphocytes (immunosuppression) and lymphoid neoplastic cells (anti-tumour). Its action is slow and relatively gentle compared with cyclophosphamide, giving gradual, predictable myelosuppression without the acrolein-mediated bladder toxicity (it has no haemorrhagic-cystitis risk).

Formulations and products

• 2 mg tablet (Leukeran)
• Leukeran — 2 mg tablet, Tablet (cytotoxic — refrigerate) (human-label)

Storage

Tablets: REFRIGERATE (2–8 °C) per label, protect from light/moisture; handle as a hazardous cytotoxic (gloves), do not crush/split tablets, dispose appropriately.

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.

Other hormones, emergency drugs, supplements and other drugs

• Calcium EDTA (Calcium Disodium Edetate)
• Carbimazole
• Carboplatin
• Cetirizine
• Chlorpheniramine Maleate
• Clenbuterol
• Clomipramine
• Clopidogrel

Frequently asked questions