Efficacy of Opioids and Mexiletine for the Treatment of Postamputation Pain
Condition: Amputation; Chronic Pain
MeSH terms: Chronic Pain
Study type: Interventional
Phase: Phase 2

Summary: 
      Persistent pain occurs in 50-85 percent of patients who experience the amputation of an
      extremity. This study will compare the effectiveness of morphine and mexiletine to placebo in
      the treatment of postamputation pain.

      It is hypothesized that the effects of opioids and mexiletine on behavior and mental
      functioning in patients with postamputation pain are unlikely to be significant barriers to
      the clinical use of the drugs.
    

Detailed description: 
      The long-term objective of this research is to develop better clinical strategies for
      alleviating pain resulting from amputation of extremities. Amputation is the most radical
      form of nerve injury. The two major types of postamputation painful sequela are phantom pain
      and stump pain. Phantom pain has been defined as painful sensation perceived in the missing
      body part, or portion thereof (Merskey and Bogduk,1994). Phantom pain is the most
      distressing, and often difficult to treat, chronic neuropathic pain syndrome that results
      from direct injury to the peripheral or central nervous system. Recent epidemiological
      studies indicate that 50-85% of patients experience persistent pain following amputations.
      This controlled clinical trial will examine the role of opioid analgesics and local
      anesthetics in the treatment of phantom and associated stump pain resulting from amputations.
      Specifically, our objectives are to answer the following questions:

        1. Does therapy with opioids and mexiletine result in better management of postamputation
           pain than treatment with placebo? Using a randomized, blinded, crossover clinical trial,
           the effectiveness of therapy with the opioid, morphine, and the oral local anesthetic,
           mexiletine, will be compared with placebo in the management of phantom and associated
           stump pain following amputations. The effectiveness of the treatment regimens will be
           judged by improvements in: a) The intensity of ongoing, stimulus-independent pain using
           established pain intensity and pain relief scales, b) Stimulus-evoked pain using
           quantitative sensory tests, and c) Impairment of function using established measures.

        2. What are the relative effects of opioids and mexiletine on affective and cognitive
           function in patients with amputated extremities? Using established tests of
           neuropsychological function, mood, and psychosocial and physical impairment, affective
           and cognitive changes associated with the opioid and mexiletine therapies will be
           quantified and compared with changes associated with placebo treatment. These studies
           will help determine if the effects of opioids and mexiletine on affect and cognition are
           likely to limit the usefulness of the medications in the treatment of pain following
           amputations.
    

Intervention name(s): morphine and mexiletine
Intervention type(s): Drug
Intervention MeSH terms: Mexiletine; Morphine
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double
Primary purpose: Treatment
Keywords: postamputation pain; phantom pain; stump pain; neuroma pain; opioid; mexiletine