An intrathecal pump is a medical device used to deliver medication directly into the spinal fluid. This method allows for smaller doses of medication to be effective, reducing side effects compared to oral or intravenous administration. It is often used for managing chronic pain or severe spasticity in conditions like multiple sclerosis. The pump is surgically implanted under the skin, typically in the abdomen, and is connected to a catheter that leads to the intrathecal space around the spinal cord. Patients can have their medication adjusted or refilled through a small port in the pump, making it a flexible option for long-term treatment.