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Peripherally administrated morphine attenuates capsaicin-induced mechanical hypersensitivity in humans
E Kinnman1, E B Nygårds, P Hansson
1Department of Rehabilitation Medicine, Karolinska Institute/Hospital, Stockholm, Sweden.
Anesthesia and Analgesia
|March 1, 1997
Summary
Peripheral morphine injections reduced mechanical hypersensitivity and pain in a capsaicin model. This suggests morphine can modulate sensitization mechanisms, offering potential for pain management strategies.
Area of Science:
- Pain research
- Neuroscience
- Pharmacology
Background:
- Peripheral administration of opioids like morphine is explored for pain modulation.
- The human capsaicin model effectively induces pain and hypersensitivity, mimicking inflammatory pain states.
Purpose of the Study:
- To investigate if peripheral morphine can modulate pain and hypersensitivity/allodynia.
- To assess morphine's effect on capsaicin-induced pain and mechanical sensitivity in humans.
Main Methods:
- Participants received subcutaneous injections of morphine or saline in separate arms before capsaicin administration.
- Pain intensity, mechanical sensitivity (von Frey filaments), pressure pain thresholds, and flare area were assessed.
- Numerical rating scales and mapping techniques were employed to quantify pain and hypersensitivity.
Main Results:
- Capsaicin induced similar spontaneous pain levels in both morphine and saline-treated arms.
- Significantly reduced pain evoked by mechanical stimuli was observed on the morphine-injected side.
- A smaller area of mechanical hypersensitivity and flare was noted following peripheral morphine administration.
Conclusions:
- Peripheral morphine effectively modulates capsaicin-induced mechanical hypersensitivity.
- Morphine may act on peripheral sensitization mechanisms contributing to pain development.
- These findings support the potential of peripheral morphine for managing certain types of pain.