Low-Dose Intrathecal Morphine Improves Multidimensional Pain Inventory Scores

AUSTIN, TXIntrathecal morphine has been increasingly used for the management of chronic non-cancer pain. At the American Pain Society's 30th Annual Scientific Meeting, Michael Harned, MD, and colleagues from the University of Kentucky, Lexington, presented study data demonstrating that low-dose intrathecal morphine improves both Numeric Pain Rating Scale (NPS) scores and Multidimensional Pain Inventory (MPI) scores in patients with chronic non-cancer pain.

The NPS assesses analgesic efficacy, quantified by pain intensity, and compares results across different treatments. It does not, however, address functional state. The MPI is a validated instrument that evaluates a number of dimensions of the chronic pain experience, including pain intensity, activity level, emotional distress, cognitive and functional adaptation, and social support. Study investigators used a combination of the NPS and the MPI to examine patient outcomes and determine patient suitability for low-dose opioid intrathecal drug delivery.

Prior to initiation of intrathecal opioid therapy, 22 patients completed the NPS and MPI as part of their overall evaluation. A second MPI was mailed to the patients 12 months following intrathecal drug delivery system implantation. Eleven patients returned a completed MPI along with a current NPS. Patients had an initial decrease in NPS from 7.18 to 3.18 (P<0.001 paired t test). At 12 months, NPS remained significantly lower compared with post-implantation measures. Significant improvement in MPI scores (50.4 pre-intrathecal opioids to 39.5 at 12 months [P<0.001 paired t test]) was also observed. Intrathecal morphine doses remained stable with an average starting dose of 0.188mg/day and an average 12-month follow up dose of 0.396mg/day.

Results from the study, Dr. Harned states, suggest that low-dose intrathecal morphine is effective in reducing pain intensity, as observed by the improved NPS scores, and may also positively impact function and coping skills in patients with chronic non-cancer pain as assessed by the MPI.

“Using MPI as an adjunct to NPS provides a more comprehensive approach and further validity in assessing patient outcomes,” he said.