Pharmacology of intrathecally administered agents for treatment of spasticity and pain

Abstract

Significant advances in the management of intractable pain and spasticity have occurred over the past two decades. This was largely a direct result of the discovery of spinal sites of action of the various analgesic and anti-spasticity agents and the clinical application of the intrathecal route for delivery of these centrally acting agents. Only two agents are FDA-approved for intrathecal use—namely morphine for intractable pain and baclofen for spasticity. However, a number of other intrathecal agents are used routinely in clinical practice, while other agents are considered experimental or unproven and are used sparingly or are regarded largely as being unsafe. The pharmacology of standard and investigational agents used intrathecally is reviewed in this article with particular attention to the mechanism of action, pharmacokinetics, indications for use, and evidence of clinical efficacy and safety profile.