What is the preferred cytotoxic drug to be used in cats?

• A. Chlorambucil
• B. Cyclosporine
• C. Azathioprine
• D. Cyclophosphamide

Answer: (A)

Chlorambucil is favored in cats because it’s an oral alkylating chemotherapy agent that suits long-term outpatient treatment, especially for feline gastrointestinal lymphoma that tends to be low-grade. Cats often tolerate chlorambucil better than other cytotoxic drugs, with milder bone marrow suppression and a lower risk of irritating the urinary tract compared with cyclophosphamide. When used with prednisone, it can achieve durable remissions in many cats with intestinal lymphoma, making it a practical and effective first choice in this setting.

Cyclophosphamide, azathioprine, and cyclosporine are associated with higher risks or different roles in feline medicine. Cyclophosphamide can cause hemorrhagic cystitis and systemic toxicity; azathioprine may lead to bone marrow suppression and liver issues; cyclosporine is an immunosuppressant rather than a cytotoxic chemotherapy agent.