Which drugs are most commonly used for intrathecal chemotherapy?

• A. Cisplatin and Carboplatin
• B. Methotrexate and Cytarabine
• C. Vincristine and Paclitaxel
• D. Bevacizumab and Etoposide

Answer: (B)

Delivering chemotherapy directly into the cerebrospinal fluid is done to treat or prevent cancer cells in the CNS by bypassing the blood–brain barrier and achieving drug exposure right at the meninges and CSF. The two drugs most commonly used this way are methotrexate and cytarabine because they have proven effectiveness against CNS leukemia and lymphoma and have established, safer intrathecal dosing regimens that achieve meaningful CSF concentrations with manageable toxicity. They’re chosen for their ability to act on malignant cells in the CSF without the systemic toxicities that complicate other routes.

Other agents listed are not routinely used intrathecally for several reasons. Platinum compounds can cause severe inflammatory and neurotoxic reactions when given into the CSF, making them less suitable for routine intrathecal use. Vincristine is notoriously dangerous if given intrathecally and has caused fatal outcomes, so it is not used this way. Paclitaxel, Bevacizumab, and many other systemic agents lack established, safe intrathecal profiles or are not formulated for effective CSF delivery.