Vinca alkaloids
Summary
Vinca alkaloids, vincristine and vinblastine, are antimitotic chemotherapy agents derived from the periwinkle plant that bind tubulin and prevent microtubule polymerization, arresting cells in M phase. Vincristine's dose-limiting toxicity is peripheral neuropathy and vinblastine's is myelosuppression.
Detail
By binding beta-tubulin at the vinca domain, these agents block assembly of the mitotic spindle, so chromosomes cannot align or segregate. This is the opposite mechanism to the taxanes, paclitaxel and docetaxel, which hyperstabilize microtubules and prevent their disassembly; both classes arrest mitosis. The toxicity split is a favourite exam point and is captured by the mnemonic that vinCRIStine is neurotoxic and hits the CRISp nerves while vinBLASTine BLASTs the bone marrow. Vincristine causes a length-dependent sensorimotor and autonomic neuropathy with loss of ankle reflexes, paraesthesiae, constipation, and ileus, and is therefore attractive in regimens where marrow reserve is limited, such as CHOP for lymphoma and induction for acute lymphoblastic leukaemia. Vincristine also causes SIADH. Both are potent vesicants causing severe tissue necrosis on extravasation. Critically, vinca alkaloids are fatal if given intrathecally, and administration protocols mandate that they are dispensed in minibags and never in a syringe.
Sources
- Katzung Basic and Clinical Pharmacology
- First Aid for the USMLE Step 1
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.