intrathecal

Intrathecal describes administration or a location within the thecal sac surrounding the spinal cord and brain, specifically the subarachnoid space filled with cerebrospinal fluid (CSF). The term is often used to distinguish this route from intraventricular or epidural administration.

Clinical use includes spinal anesthesia, where local anesthetics are injected into the intrathecal space to produce a rapid, regional loss of sensation and movement for surgical procedures. Intrathecal analgesia may involve opioids or other agents added to provide pain relief postoperatively. In medicine, certain drugs are given intrathecally to bypass the blood-brain barrier and treat diseases of the CSF, most notably chemotherapeutic agents such as methotrexate, cytarabine, and thiotepa, for meningeal leukemia, lymphoma, or carcinomatosis. It is also used, in selected cases, for antibiotics, enzymes, or diagnostic/contrast agents delivered directly into CSF.

Procedure and considerations involve placing a needle into the intrathecal space via lumbar puncture or through an implanted catheter. Solutions are typically preservative-free and prepared for intrathecal use. Dosing and distribution differ from systemic therapy due to CSF dynamics, and careful aseptic technique and monitoring are essential. Spinal anesthesia is usually performed in a controlled surgical setting, often with the patient in a seated or lateral position.

Risks and adverse effects include post-dural puncture headache, infection such as meningitis, bleeding, or nerve injury. Chemical meningitis or arachnoiditis can occur with certain agents, and there can be systemic toxicity if drugs inadvertently enter the bloodstream.

Overall, intrathecal therapy provides targeted delivery to the CSF compartment, balancing potential benefits with procedure- and drug-related risks.