Medicines are delivered to the intrathecal space. This is a fluid filled area which cushions the spinal cord. The sac which contains the fluid is called the dura mater (see diagrams below), and is contained within the epidural space. The epidural space, dura mater, and spinal cord is all surrounded and protected by the bones of your spine. The fluid which fills the dura is called cerebral spinal fluid (CSF), and intrathecal medicines are delivered to this fluid, ultimately being absorbed by the spinal cord.