Chlorambucil

What is this medication for?

• Chronic low-grade intestinal lymphoma (with prednisolone); refractory/severe IBD; pemphigus foliaceus; eosinophilic granuloma complex — preferred over cyclophosphamide/azathioprine for cat safety
• Lymphocytic leukemia, multiple myeloma, polycythemia vera, macroglobulinemia; immunosuppression (glomerulonephritis 0.1–0.2 mg/kg q24–48h; alternative in IMHA/immune disease)

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• The 2 mg tablet is a convenient cat-sized dose — the every 2 days-vs-every 3 days (>4 kg vs <4 kg) split is the practical dosing pearl.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• Myelosuppression (mild, gradual) (Lower than cyclophosphamide — the point of choosing it)

Worth a phone call to your veterinarian

• stomach/intestinal toxicity, loss of appetite (Occasional)
• Rare neurologic signs (myoclonus reported — human) (Uncommon)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Preexisting marrow depression; active infection; prior resistance to alkylators

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Other myelosuppressives
  • Prednisolone

Storage and handling

Refrigeration often recommended (tablets); chemo-glove handling; keep in original blister.

Good to know

• Chlorambucil is the cat's alkylator: slow, oral, low-marrow-toxicity — the backbone of small-cell intestinal lymphoma therapy (with pred) and steroid-refractory IBD.
• Cyclophosphamide → hemorrhagic cystitis and harsher marrow hits; chlorambucil → none of the bladder risk — the swap rationale in chronic feline therapy.
• The 2 mg tablet is a convenient cat-sized dose — the every 2 days-vs-every 3 days (>4 kg vs <4 kg) split is the practical dosing pearl.
• Polycythemia vera and multiple myeloma: the quieter chronic indications alongside the stomach/intestinal ones.