Intrathecal baclofen refers to direct delivery of the anti-hypertonia drug baclofen into the spinal fluid space. This method of delivery enables a higher concentration of the drug to be injected at the treatment target site within the spinal cord, while avoiding high concentrations in the brain and upper spinal cord, where the drug can have undesired side effects, such as lethargy and respiratory depression. A surgically implanted drug reservoir with a pump delivers a small amount of the drug directly into the spinal fluid space in the upper, mid-, or lower back. This system typically delivers drug concentrations 100 times higher at the point where the drug exits the catheter than in the brain. This means that much higher concentrations than when the same medication is taken by mouth can reach the target sites within the spinal cord without the worry of undesired side effects elsewhere in the body