intrathekal

Intrathecal, also spelled intrathekal, refers to administration within the intrathecal space, the subarachnoid space surrounding the spinal cord and enclosed by the meninges. This route delivers drugs directly into cerebrospinal fluid (CSF), achieving high central nervous system exposure with relatively lower systemic concentrations.

Delivery methods can include a one-time lumbar puncture for injection or an implanted intrathecal drug delivery system (IDDS) with a catheter connected to a programmable pump that provides continuous or intermittent dosing. Intrathecal therapy is commonly used when systemic treatment is ineffective or poorly tolerated.

Indications and agents: The intrathecal route is used for management of severe, refractory pain (including cancer-related pain) and for spasticity due to spinal cord injury, multiple sclerosis, or cerebral palsy. Intrathecal chemotherapy is employed for leptomeningeal metastases. Drugs delivered intrathecally include opioids (such as morphine and fentanyl), local anesthetics (such as bupivacaine and ropivacaine), and other agents like baclofen and ziconotide. Drug selection and dosing depend on the underlying condition, drug properties, and patient response.

Safety and complications: Potential risks include infection at the catheter or pump site, meningitis, arachnoiditis, CSF leak, catheter obstruction, pump malfunction, and overdose with respiratory depression or neurotoxicity. Under-dosing can fail to control symptoms. Careful patient selection, sterile technique, and close monitoring are essential, along with regular maintenance of implanted devices and dose titration.

History and note: The intrathecal route has a long history in anesthesia, pain management, and oncology, with ongoing advances in delivery systems and pharmacology.