Vincristine

What it is used for

• Neoplastic diseases
• Neoplastic diseases (particularly lymphoproliferative disorders)
• Neoplastic diseases
• Neoplastic diseases (usually in combination protocols)
• Transmissible venereal tumor (TVT)
• Adjunctive treatment of immune-mediated thrombocytopenia (IMT)
• Adjunctive treatment of immune-mediated thrombocytopenia (IMT) refractory to prednisone
• Adjunctive treatment of immune-mediated thrombocytopenia (IMT)
• Neoplastic diseases (particularly lymphoproliferative disorders), immune-mediated thrombocytopenia, transmissible venereal tumour

How it is given

Possible side effects

• Peripheral neuropathy (proprioceptive deficits, spinal hyporeflexia)
• Paralytic ileus and severe constipation
• Mild leukopenia
• Tissue necrosis and sloughing (if extravasated)
• Anorexia, vomiting, diarrhea
• Impaired platelet aggregation
• Increased liver enzymes
• Syndrome of inappropriate ADH secretion (SIADH)
• Jaw pain
• Alopecia
• Stomatitis
• Seizures
• Pulmonary edema (rare, reported in cats)
• Peripheral neuropathy

Cautions & contraindications

• Preexisting neuromuscular disease
• Severe leukopenia
• Uncontrolled infection
• No specific absolute contraindications listed, but requires extreme caution in specific disease states
• > **Extravasation Warning**: Vincristine is a potent vesicant. It must be given strictly IV. Use a different needle for injection than the one used to draw the drug from the vial. If extravasation occurs, stop immediately, apply moderate heat (or ice, depending on protocol), and consider topical DMSO or hyaluronidase injections. * **ABCB1 (MDR1) Mutation**: Herding breeds (e.g., Collies, Australian Shepherds) with this mutation are highly susceptible to severe bone marrow suppression and GI toxicity. Reduce dose by 25-30% in mutant/normal or mutant/mutant dogs. * **Hepatic Impairment**: Extensively metabolized by the liver. Consider a 50% dose reduction if serum bilirubin is > 2 mg/dL. * **Neurotoxicity**: Cats are particularly sensitive to neurotoxicity, which can manifest as paralytic ileus, severe constipation, and reversible axon swelling. * **Handling**: Wear gloves and protective clothing. Wash thoroughly with soap and water if skin exposure occurs. * **Pregnancy**: Potentially teratogenic and embryotoxic (FDA Category D).

Drug interactions

• Asparaginase: Additive neurotoxicity may occur; less common if asparaginase is administered after vincristine.
• Mitomycin: Severe bronchospasm has occurred in humans receiving mitomycin-C with Vinca alkaloids.
• Amiodarone: Inhibits P-glycoprotein; may increase vincristine toxicity, especially in MDR1/ABCB1 mutant dogs.
• Azole Antifungals (e.g., ketoconazole): Inhibits P-glycoprotein; may increase vincristine toxicity.
• Carvedilol: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Cyclosporine: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Diltiazem: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Erythromycin: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Clarithromycin: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Quinidine: Inhibits P-glycoprotein; may increase vincristine toxicity.
• Spironolactone: Inhibits P-glycoprotein; may increase vincristine toxicity.

Frequently asked questions