The pain quality response profile of oxymorphone extended release in the treatment of low back pain

Abstract

Objective: In controlled trials of analgesics, the primary outcome variable is most often a measure of global pain intensity. However, because pain is associated with a variety of pain sensations, the effects of analgesic treatments on different sensations could go undetected if specific pain qualities are not assessed. This study sought to evaluate the utility of assessing the multiple components of non-neuropathic pain in an analgesic clinical trial.

Methods: A secondary analysis was performed using data from a clinical trial involving 140 individuals with low back pain who were converted from prestudy opioids to an equianalgesic dose of an extended release (ER) formulation of oxymorphone (OPANA ER), which was then titrated to a stable dose [defined as visual analog scale <or=40 mm (0 to 100 mm) on 3 of 5 consecutive days and requiring <or=2 doses rescue medication]. Stabilized participants were then randomly assigned to continue with either oxymorphone ER or placebo for 12 weeks. A multidimensional measure of pain quality, the Pain Quality Assessment Scale (PQAS), was administered before titration, after titration, and after treatment with oxymorphone ER or placebo.

Results: Significant pretitration to posttitration decreases were observed in 17 of the 20 PQAS pain descriptor items and all 3 PQAS scales. The largest effects of oxymorphone ER were found on the PQAS intense, unpleasant, deep, aching, and sharp items and the PQAS Paroxysmal and Deep scales.

Discussion: The results indicate that oxymorphone ER has different effects on different pain qualities of low back pain. The responsivity of the PQAS items and scales to the results of treatment with an effective and generally well-tolerated dose of an analgesic, and the ability of the PQAS items and scales to discriminate between an active analgesic and placebo, support their validity as outcome measures. The findings support the utility of using pain descriptor measures for (1) identifying the effects of pain treatments on different pain qualities and (2) targeting pain treatments to those patients who experience certain types of pain.