Vinblastine

What is this medication for?

• Lymphoma (combination protocols), mast cell tumors (more effective than vincristine), carcinomas, splenic tumors, transmissible venereal tumor
• Lymphoma and other neoplasms in combination protocols

How is it given?

This medication is normally given by your veterinary team (in clinic or hospital).

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 (worse than vincristine) — low infection-fighting cell counts nadir ~day 4–7 (Dose-limiting)
• Gastroenterocolitis (nausea/vomiting/diarrhea), mouth sores, constipation, alopecia (Common)
• Jaw/muscle pain, loss of deep tendon reflexes (Chronic use)

Worth a phone call to your veterinarian

• Neurotoxicity: constipation, paralytic ileus, loss of appetite aggravation, axonal swelling/demyelination (reversible) (Cats especially)

⚠️ 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 low white blood cell counts/granulocytopenia (unless disease-related), active bacterial infection
• has or has had: Hepatic dysfunction (reduce 50%); herding breeds/MDR1 (reduce 25–30%, monitor); preexisting neuromuscular disease

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • P-gp inhibitors (cyclosporine, ketoconazole etc.)
  • Methotrexate
  • Phenobarbital

Storage and handling

Refrigerated into a vein product. Vesicant: never extravasate; gloves/protective clothing for prep and administration; wash exposures immediately.

Good to know

• Same family, opposite toxicities: vinblastine = marrow-toxic, vincristine = neuro-toxic — the classic exam contrast. Vinblastine is the MCT drug; vincristine the lymphoma/ITP drug.
• MDR1/ABCB1 herding breeds: both vincas are P-gp substrates — 25–30% dose reduction (WSU lab guidance) in mutant/mutant AND mutant/normal dogs.
• Lethal dose reported at 0.2 mg/kg in dogs — a small overdose of a tiny-volume drug; double-check the math (mg/m², not mg/kg!).
• Vesicant discipline: dedicated clean line, flush before/after, no subcutaneous leakage (tissue tissue death).