While most patients experiencing pain from cancer are able to be managed with oral opioids, there is a subset of patients who require such high doses that they experience side effects from these pain relieving medications. Such patients may be candidates for intrathecal opioids; i.e. opioids delivered directly into the spinal fluid.

Intrathecal drug infusion - This technique involves implanting a drug pump with a catheter to deliver morphine into the spinal fluid space around the spinal cord (closer to the pain receptors than epidural injections). To provide the same pain relief, intrathecal morphine requires a much lower dosage than oral, intra-muscular, intra-venous or an epidural injections and consequently has much less systemic side effects.