Spinal mechanisms of pain and analgesia.

Chronic pain--especially that which is refractory to conventional treatment--presents particular challenges to physicians and patients. Examination of the molecular and cellular mechanisms involved in this pathophysiology suggests that spinal instillation of therapeutic agents may offer an effective treatment option through the modification of the processing and sensation of chronic pain. Intrathecal therapy, used alone or in combination with other analgesic agents, may reduce chronic pain by attenuating both pre- and postsynaptic activities. This article reviews chronic pain pathophysiology and the mechanisms whereby spinally administered analgesics may modify chronic pain. Available treatment options are also considered, including recommendations from the 2007 Polyanalgesic Consensus Conference (PACC) guidelines on the use of intrathecal agents for nociceptive, neuropathic, and mixed pain.