Background: Intrathecal drug infusion therapy is usually considered when spinal-acting analgesics or antispasmodics administered via the oral or transdermal routes fail to control patients' pain or are associated with unacceptable side effects. The intrathecal administration of centrally acting agents bypasses the blood-brain-barrier resulting in much higher cerebrospinal fluid (CSF) concentrations while using reduced amounts of medication to achieve equipotent doses. The intrathecal approach is associated with higher rates of satisfactory pain relief and lower rates of treatment failures and technical complications compared to the epidural route. A paucity of randomized controlled trials (RCTs) has led to concern regarding proper use, selection criteria, and safety of these devices. Cost effectiveness and comparative therapies have now also become a focus of discussion.
Objective: The purpose of this systematic review is to evaluate and update the available evidence for the efficacy and safety of intrathecal infusions used in long-term management (> 6 months) of chronic pain. This paper will not focus on intrathecal administration for spasticity or movement disorders.
Study design: A systematic review of intrathecal infusion through implanted drug delivery devices for chronic pain.
Methods: Literature search through EMBASE, Medline, Cochrane databases, and systematic reviews as well as peer-reviewed non-indexed journals from 1980 to December 2010. Studies are assessed using the Agency for Healthcare Research and Quality (AHRQ) criteria for observational studies and the Cochrane Musculoskeletal Review Group criteria for randomized trials. The level of evidence was determined using 5 levels of evidence, ranging from Level I to III with 3 subcategories in Level II, based on the quality of evidence developed by the U.S. Preventive Services Task Force (USPSTF).
Outcome measures: The primary outcome measure for chronic non-cancer is pain relief (short-term relief ≤ one-year and long-term > one-year), whereas it is 3 months for cancer. Secondary outcome measures of improvement in functional status, psychological status, return to work, and reduction in opioid intake.
Results: The level of evidence for this systematic review of non-cancer pain studies meeting the inclusion criteria of continuous use of an intrathecal drug delivery system (IDDS) for at least 12 months duration with at least 25 patients in the cohort, is Level II-3 based on USPSTF criteria. The level of evidence for this systemic review for cancer-related pain studies meeting the inclusion criteria of continuous use of IDDS for at least 3 months duration with at least 25 patients in the cohort is Level II-2 based on USPSTF criteria.
Conclusion: Based on the available evidence, the recommendation for intrathecal infusion systems for cancer-related pain is moderate recommendation based on the high quality of evidence and the recommendation is limited to moderate based on the moderate quality of evidence from non-randomized studies for non-cancer related pain.