Background: Methadone and ketamine are used in neuropathic pain management.
However, the benefits of both drugs association are uncertain in the treatment of
neuropathic pain.
Objective: Our primary objective was test the hypothesis that oral methadone
combined with oral ketamine is more effective than oral methadone or ketamine alone
in reducing neuropathic pain.
Study Design: We conducted a randomized, double blind, active-controlled parallelgroup clinical trial.
Methods: Forty-two patients with neuropathic pain refractory to conventional therapy
were randomly assigned to receive oral methadone (n = 14), ketamine (n = 14), or
methadone plus ketamine (n = 14) over a 3-month period.
Results: During these 90 days, we observed pain scores using a visual analogical scale
(VAS), allodynia, burning/shooting pain, and some side effects. All treatments were
effective in reducing pain scores by at least 40%. However, a significant improvement in
pain was observed only in the ketamine alone group compared with both the methadone
or methadone/ketamine groups. No significant differences were observed among the
treatment groups for the reduction of burning or shooting pain, while ketamine alone
was more effective than methadone or methadone/ketamine for the reduction of
allodynia.
Limitations: Formal assessment for awareness of the allocation was not performed,
some co-intervention bias may have occurred, our results could be only relevant to the
patient population investigated and the use of VAS as the primary outcome detect
changes in pain intensity but not to assess neuropathic pain symptoms.
Conclusion: This study indicates that ketamine was better than methadone or
methadone/ketamine for treating neuropathic pain.
Key words: Multimodal analgesia, refractory pain, NMDA receptor, opioid
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