Treatment options for refractory pain: the role of intrathecal therapy.

Intraspinal drug delivery represents an important treatment option for the management of chronic pain. Selection of candidates for this type of therapy requires careful evaluation of the patient, possibly including psychological screening. Although determining the efficacy of long-term intraspinal drug therapy has been challenging, several classes of agents have been identified to provide benefits in patients with a variety of pain types. Such agents include opioids, alpha(2)-agonists, sodium channel antagonists, and gamma-aminobutyric acid agonists. In addition, combinations of agents with distinct mechanisms of action may be therapeutically advantageous because many clinical pain states result from more than one mechanism.