Which drug is fatal if given intrathecally?

Vincristine is considered fatal if given intrathecally because it is not formulated for that route of administration and can cause severe neurotoxicity leading to rapid neurological impairment and death. The CNS is especially sensitive to the neurotoxic effects of vincristine, and administration through the intrathecal route bypasses normal distribution and elimination pathways, resulting in a concentrated toxic effect on the central nervous system.

In clinical practice, vincristine is intended for intravenous use, where it effectively treats various cancers by disrupting the microtubules necessary for cell division. However, the devastating consequences of an intrathecal administration underscore the critical need for proper handling and administration routes for chemotherapeutic agents.

Other options, while also chemotherapeutic agents, do not share the same fatal risk when administered intrathecally. Vinblastine and the taxanes, paclitaxel and docetaxel, have different safety profiles and routes of administration that do not carry the same level of neurotoxic risk when given intrathecally.