Vincristine

What is this medication for?

• Lymphoid/hematopoietic neoplasms (combination protocols — CHOP backbone); transmissible venereal tumor (sole therapy); immune-mediated low platelet counts (adjunct — thrombocytosis effect)

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 (Much less than vinblastine)

Worth a phone call to your veterinarian

• Peripheral neurotoxicity > vinblastine: proprioceptive deficits, spinal hyporeflexia, paralytic ileus/constipation (Dose/cumulative)
• Stomatitis, alopecia (minimal in dogs/cats), inappropriate ADH secretion (Occasional)

⚠️ 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: Hepatic disease (−50% if bili >2); low white blood cell counts/infection; preexisting neuromuscular disease; MDR1 herding breeds — same P-gp caution as vinblastine

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • P-gp inhibitors
  • L-asparaginase
  • Other myelosuppressives

Storage and handling

Refrigerated. Vesicant — same handling rules as vinblastine (gloves, clean line, no extravasation).

Good to know

• The vincristine trio of tricks: CHOP lymphoma workhorse, TVT cure-in-a-vial, and a platelet bump for ITP (0.02 mg/kg once — pairs with prednisone; efficacy debated but traditional).
• Constipation/ileus after vincristine in a cat = neurotoxicity, not "just stomach/intestinal upset" — anticipate (lactulose/stool softeners).
• mg/m² dosing (NOT mg/kg): a 30 kg dog gets ~0.6 m² → ~0.4 mg; a decimal error is a 10× overdose (cat lethal = 0.1 mg/kg).
• Extravasation = tissue tissue death: free-flowing into a vein catheter, flush before and after.