Which administration route is used to deliver chemotherapy to treat central nervous system disease?

• A. Intravenous
• B. Oral
• C. Intraperitoneal
• D. Intrathecal

Answer: (D)

Delivering chemotherapy to the central nervous system requires bypassing the blood-brain barrier, which limits how much drug reaches the CSF when given systemically. Intrathecal administration delivers the drug directly into the cerebrospinal fluid, usually via lumbar puncture or an implanted reservoir, achieving high local concentrations around the brain and spinal cord where malignant cells may be present. This route is used specifically to treat CNS involvement by cancers (such as meningitis carcinomatosis from leukemia or lymphoma) or to prophylax against CNS disease because systemic therapy often doesn’t reach effective CSF levels. In contrast, intravenous and oral routes rely on systemic circulation and must cross into the CNS, which is limited by the blood-brain barrier, while intraperitoneal administration targets the peritoneal cavity. Intrathecal agents commonly include methotrexate, cytarabine, and thiotepa. Potential risks include chemical meningitis, neurotoxicity, headaches, and infection from the delivery device, so careful technique and monitoring are essential.