What is the role of intrathecal (in the spinal canal) opioids in managing severe pain?

Role of Intrathecal Opioids in Managing Severe Pain

Intrathecal opioid delivery should be considered for patients with severe, refractory pain who have failed conventional pain management strategies, particularly those with cancer pain or intractable non-cancer pain with life expectancy >6 months. 1

Indications for Intrathecal Opioid Therapy

• Intrathecal opioid administration should be considered in patients experiencing pain in various anatomic locations including head and neck, upper and lower extremities, and trunk 1
• Most appropriate for patients with:
  • Inadequate pain relief despite systemic opioid dose escalation 1
  • Non-effective response to opioid switching or route changes 1
  • Intolerable side effects from systemic opioid therapy 2
  • Life expectancy >6 months (for implantable pump systems) 1

Advantages of Intrathecal Route

• Significantly reduced opioid dosing requirements:
  • Intrathecal route requires only 1/10 of systemic dose for equivalent analgesia 1
  • Epidural route requires 20-40% of systemic dose 1
• Better pain control with fewer systemic side effects due to proximity to receptor sites 3
• Lower risk of infection compared to epidural route 1
• Fewer catheter problems compared to epidural delivery 1
• Less affected by presence of extensive epidural metastasis 1

Delivery Methods

• Delivery options include:
  • Percutaneous catheters (temporary) 1
  • Tunneled catheters 1
  • Implantable programmable pumps 1
• Fully implanted systems offer less infection risk and lower maintenance requirements but involve more complex positioning 1

Patient Selection and Trial Period

• A trial period is strongly recommended before permanent implantation 1
• Trial options include:
  • Temporary epidural or spinal catheter 1
  • Single-shot intrathecal trial 1
• Successful trial defined as >50% pain reduction 3, 4
• Contraindications include:
  • Active infection 1
  • Coagulopathy 1
  • Very short life expectancy 1

Medications Used Intrathecally

• Primary medications:
  • Morphine (most commonly used) 1
  • Ziconotide 1
  • Baclofen (particularly for spasticity) 1
• Adjuvant medications:
  • Local anesthetics (bupivacaine 0.125%-0.25%) 1
  • Limited evidence supports subanesthetic doses of ketamine for intractable pain 1

Efficacy

• Cancer pain: Better pain control and fewer side effects compared to oral/transdermal treatment 2
• Non-cancer pain: Long-term studies show 57-67% pain reduction at follow-up 4, 5
• Best results seen in:
  • Deafferentation pain (75% reduction) 4
  • Mixed pain (61% reduction) 4
  • Nociceptive pain (initial 78% reduction, decreasing to 57% over time) 4

Complications and Side Effects

• Technical complications:
  • Catheter problems (dislocation, obstruction, kinking, disconnection, rupture) 3, 6
  • Pump malfunctions (rare with newer models) 3, 6
• Biological complications:
  • Infection 6
  • Granuloma formation at catheter tip (can cause neurological damage) 2, 6
• Drug-related side effects:
  • Generally fewer systemic side effects than oral administration 3
  • Dose escalation may be required over time, particularly in non-cancer pain 4, 5

Clinical Recommendations

• Intrathecal techniques should be included as part of cancer pain management strategy but widespread use should be avoided 1
• Intrathecal delivery should be monitored by a skilled team 1
• For non-cancer pain, careful patient selection is critical as outcomes may vary 5
• Pump implantation should only be performed in specialized centers with expertise in this technique 3

Practical Considerations

• Catheter tip position significantly influences clinical effect due to uneven distribution of medication in CSF 3
• Dose adjustments are typically required over time, especially in non-cancer pain patients 4, 5
• Mean serum/CSF concentration ratio for morphine is approximately 1:3000, explaining low rate of systemic side effects 3