Vet Guide to Chlorambucil in 2025 🐾

Hi, I’m Dr Duncan Houston, BVSc—founder of Ask A Vet. In this in-depth 2025 guide, we explore chlorambucil—a powerful oral chemotherapy and immunosuppressant. It’s used to manage cancer (like lymphoma, leukemia) and immune-mediated diseases in dogs and cats. Learn dosing strategies, safety measures, handling precautions, side effects, and lab monitoring to support your pet’s treatment journey. 🩺

📘 What Is Chlorambucil?

Chlorambucil (brand name Leukeran®) is an alkylating agent that disrupts DNA replication, slowing cancer growth and calming overactive immune responses. It’s a long-established chemotherapy drug often used in low-dose (“metronomic”) protocols :contentReference[oaicite:3]{index=3}.

✅ Common Uses in Pets

• **Low-grade lymphoma or leukemia** in dogs and cats :contentReference[oaicite:4]{index=4}
• **Gastrointestinal lymphoma** in cats—often paired with prednisolone :contentReference[oaicite:5]{index=5}
• **Immune-mediated conditions** like IMHA, pemphigus, eosinophilic granuloma in cats :contentReference[oaicite:6]{index=6}
• **Metronomic chemo** in dogs: low-dose daily or every-other-day supports tumor control with fewer side effects :contentReference[oaicite:7]{index=7}

📐 Dosing & Administration

• **Dogs:** ~0.05–0.1 mg/lb (0.1–0.2 mg/kg) daily for 1–2 weeks, then taper to lower maintenance or every 48–72 hrs :contentReference[oaicite:8]{index=8}.
• **Cats:** 0.05–0.1 mg/lb daily, or 0.25–0.5 mg/lb every 48–72 hrs, based on tolerance :contentReference[oaicite:9]{index=9}.
• Tablets are given **with food** to minimize GI upset. Liquid forms may be compounded for dosing ease :contentReference[oaicite:10]{index=10}.

⏱️ Timing & Onset

Effects take days to weeks. In cats with GI lymphoma, pulse-dosing combined with prednisolone often shows improvement within 1–2 weeks :contentReference[oaicite:11]{index=11}. Metronomic regimens focus on tumor stabilization rather than remission :contentReference[oaicite:12]{index=12}.

⚠️ Side Effects & Risks

Common:

• Bone marrow suppression—low blood cell counts, infection, bleeding risk :contentReference[oaicite:13]{index=13}
• GI upset—vomiting, diarrhea, appetite loss, lethargy :contentReference[oaicite:14]{index=14}
• Alopecia—especially in Poodles and Kerry Blues :contentReference[oaicite:15]{index=15}

Serious:

• Seizures, severe bleeding, respiratory distress :contentReference[oaicite:16]{index=16}
• Liver or kidney enzyme elevations :contentReference[oaicite:17]{index=17}
• Potential infertility in males :contentReference[oaicite:18]{index=18}

🧤 Safe Handling at Home

• Wear gloves when handling tablets and pet waste for 48 hrs post-dose :contentReference[oaicite:19]{index=19}
• Avoid contact with drug and pet saliva/urine/feces. Dispose waste sealed in plastic :contentReference[oaicite:20]{index=20}
• Pregnant or immunocompromised individuals should not handle or be near contaminated materials :contentReference[oaicite:21]{index=21}

🔗 Drug Interactions & Contraindications

• Avoid concurrent myelosuppressants, alkylating agents, certain immunosuppressants, amphotericin B, and live vaccines :contentReference[oaicite:22]{index=22}
• Pre-existing bone marrow suppression or infections are contraindications :contentReference[oaicite:23]{index=23}

🩺 Monitoring & Follow‑Up

• Baseline CBC, blood chemistry, urinalysis prior to starting :contentReference[oaicite:24]{index=24}
• Recheck CBC & chemistry every 1–3 months (or more frequently with active dosing) :contentReference[oaicite:25]{index=25}
• Monitor for blood in stool/urine, fever, appetite loss, bleeding, neurological signs

❓ FAQs

Can I skip a dose?

No—dosing schedules are critical. If you miss a dose, contact your vet. Do not double doses :contentReference[oaicite:26]{index=26}.

Is chlorambucil risky long-term?

Chronic use increases marrow suppression risk but metronomic protocols are well tolerated with regular monitoring :contentReference[oaicite:27]{index=27}.

Can pregnant pets take it?

No—contraindicated due to teratogenic risks. Handle all exposures with caution :contentReference[oaicite:28]{index=28}.

Should I avoid vaccines?

Yes—live vaccines are contraindicated; discuss timing of any immunizations with your vet :contentReference[oaicite:29]{index=29}.

🏡 Case Examples

🐱 Cat with GI lymphoma

• Pulse chlorambucil 0.2 mg/kg daily + prednisolone—improvement within weeks :contentReference[oaicite:30]{index=30}
• Monitor CBC every 2–3 weeks; adjust or pause as needed

🐶 Dog using metronomic dosing for mast cell tumors

• Daily low dose (~4 mg/m²) with prednisolone—stable disease and minimal side effects :contentReference[oaicite:31]{index=31}
• Monthly labs confirm marrow stability and no adverse blood counts

📌 Final Takeaways

• Chlorambucil is a vital oral chemo/immunosuppressant for cancer and immune conditions in pets.
• Dosing varies—pulse vs. metronomic strategies suit different diagnoses.
• It demands safe home handling, gloves, and litter/waste precautions.
• Side effects can be serious—rigorous CBC, chemistry monitoring is essential.
• Used responsibly, chlorambucil can support quality-of-life goals and disease control.

Curious about chlorambucil for your pet’s condition—or need help designing a safe treatment plan? Download the Ask A Vet app for expert dosing calculators, lab tracking tools, and 24/7 veterinary support. Together, we’ll guide your pet through treatment with care and confidence. 🐾❤️