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Evidence for analgesia mediated by peripheral opioid receptors in inflamed synovial tissue

A J Lawrence1, G P Joshi, A Michalkiewicz

  • 1Pain Research Institute, Liverpool, UK.

European Journal of Clinical Pharmacology
|January 1, 1992
PubMed

Insights

Intra-articular morphine provided post-operative pain relief after knee surgery. Local morphine administration may activate opioid receptors in the synovium for peripheral analgesia.

Area of Science:

  • Pharmacology
  • Orthopedic Surgery
  • Pain Management

Background:

  • Post-operative pain is a common complication of arthroscopic knee surgery.
  • Opioid analgesics are frequently used for pain management, but systemic administration can lead to side effects.
  • Intra-articular drug delivery offers a potential route for localized therapeutic effects.

Purpose of the Study:

  • To investigate the efficacy of intra-articular morphine for post-operative analgesia.
  • To determine plasma levels of morphine and its metabolites after intra-articular administration.
  • To assess the presence of opioid receptors in the synovial tissue.

Main Methods:

  • Patients received intra-articular morphine (5 mg) post-arthroscopic knee surgery.
  • Plasma samples were collected at intervals (30 min to 4 h) to measure morphine and metabolite levels.
  • Synovial biopsy samples were analyzed for opioid binding sites using [3H]naloxone.

Main Results:

  • Morphine and morphine-3-glucuronide were detected in 7/10 patients' plasma; morphine-6-glucuronide in 2/10.
  • Plasma morphine levels were generally below analgesic thresholds, suggesting peripheral action.
  • Opioid binding sites were identified in 6/11 synovial biopsy samples.

Conclusions:

  • Intra-articular morphine can provide post-operative analgesia following knee arthroscopy.
  • Low systemic levels suggest peripheral analgesia mediated by local action.
  • The presence of opioid receptors in the synovium supports the mechanism of action for intra-articular opioids.

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