Which route is used to deliver chemotherapy directly into the cerebrospinal fluid?

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

Answer: (A)

Directly into the cerebrospinal fluid means delivering the drug where it can act on the brain and spinal cord spaces, bypassing the protective blood-brain barrier. The intrathecal route accomplishes this by injecting chemotherapy into the CSF via a lumbar puncture or through an implanted reservoir. This approach allows higher local concentrations of drugs like methotrexate or cytarabine to treat or prevent CNS involvement from malignancy.

Other routes place the drug into the bloodstream, the gastrointestinal tract, or the peritoneal cavity and do not place it in the CSF, so they’re not effective for delivering therapy directly to CSF. Intravenous administration distributes systemically with limited CSF penetration; oral administration is swallowed and absorbed through the GI tract; intraperitoneal administration targets the peritoneal cavity.