Intrathecal administration is a medical procedure that involves delivering medication directly into the fluid surrounding the spinal cord. This method allows drugs to reach the central nervous system more directly. It is employed when systemic drug delivery, such as oral or intravenous routes, may not be effective. This targeted approach is used for various medical purposes, including pain management, chemotherapy, and addressing certain infections.
What is Intrathecal Administration?
Intrathecal administration involves injecting medication into the subarachnoid space, the area surrounding the spinal cord and brain. This space contains cerebrospinal fluid (CSF), which bathes the brain and spinal cord. Once introduced into the CSF, medication spreads throughout the central nervous system.
This method bypasses the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). These natural barriers restrict substances from the bloodstream into the brain and spinal cord, protecting these tissues. Direct introduction into the CSF allows higher medication concentrations to reach the central nervous system. This leads to more potent effects with potentially lower overall drug doses compared to systemic administration, reducing unwanted side effects elsewhere in the body.
Conditions Treated and Medications Used
Intrathecal administration treats conditions where targeted central nervous system delivery is beneficial. Common applications include managing chronic pain, such as severe non-malignant and cancer-related pain. Analgesics like opioids or local anesthetics can be delivered directly to the spinal cord to block pain signals.
The method also treats spasticity, characterized by muscle stiffness and involuntary spasms, often seen in neurological disorders like multiple sclerosis or cerebral palsy. Muscle relaxants provide relief. Intrathecal chemotherapy is used for central nervous system cancers like leukemia or lymphoma, ensuring drugs reach cancer cells directly when systemic delivery is ineffective due to the blood-brain barrier.
The Procedure and Patient Experience
Patients are positioned either curled up on their side or seated with their back rounded to open spaces between lower back vertebrae. The skin over the injection site, usually in the lumbar spine between L3-L5, is thoroughly cleaned with an antiseptic solution to prevent infection.
A local anesthetic numbs the skin, which may cause a brief stinging sensation. Once numb, a thin, hollow “spinal needle” is carefully inserted between the vertebrae into the subarachnoid space. Patients might feel pressure as the needle advances. After confirming its position, the prescribed medication is slowly injected. Following the injection, patients are advised to lie flat for several hours to minimize post-procedure headache risk.
Potential Risks and Side Effects
Potential risks and side effects exist. A common side effect is a post-dural puncture headache, or “spinal headache,” caused by a small cerebrospinal fluid leak after needle insertion. This headache usually improves with rest and hydration. Nausea and vomiting may also occur.
Less common but more serious risks include severe infection, such as meningitis. Bleeding, leading to a hematoma near the spinal cord, is another rare complication. There is also a slight risk of nerve damage, potentially causing temporary or persistent numbness, weakness, or pain. Allergic reactions to the medication are possible. Additionally, imprecise medication dosage carries a risk of drug overdose.