What is the recommended dose of morphine (opioid) for intrathecal administration?

Recommended Intrathecal Morphine Dosing

For intrathecal morphine administration, the recommended dose is 0.075-0.15 mg (75-150 μg) for single-shot administration, with doses ≤0.1 mg (100 μg) preferred to minimize adverse effects while maintaining analgesic efficacy. 1

Dosing Recommendations by Clinical Context

Postoperative Pain Management

• For elective cesarean section, intrathecal morphine at doses of 100 μg or lower is recommended, as lower doses provide adequate analgesia with reduced incidence of side effects 2
• For total hip arthroplasty, if intrathecal morphine is used, a dose of 0.1 mg (100 μg) is suggested, which provides documented analgesia for at least 24 hours postoperatively 2
• Optimal "single-shot" intrathecal morphine dose appears to be 0.075-0.15 mg based on balancing analgesic efficacy and minimizing dose-related adverse effects 1

Cancer Pain Management

• For cancer pain management using continuous intrathecal administration via implantable pumps, starting doses are typically lower (0.2-1.11 mg/day) and may increase over time 3, 4
• When compared with epidural drug delivery, intrathecal delivery requires only about 10% of the systemic dose to reach equianalgesia 2
• For cancer pain, intrathecal administration has advantages including fewer catheter problems, smaller drug dose requirements, and better pain control compared to epidural routes 2

Side Effects and Monitoring

Common Side Effects

• Pruritus and postoperative nausea and vomiting are common side effects associated with intrathecal morphine 2
• Even at low doses (≤0.1 mg), these side effects may delay ambulation and oral intake, potentially affecting patient satisfaction 2
• Other common side effects include urinary retention (38.9%) and constipation 3, 5

Respiratory Depression

• Respiratory depression is a serious potential side effect that requires careful monitoring 1
• Respiratory depression with intrathecal morphine can be slow in onset and prolonged 6
• Higher doses (1 mg and above) are associated with more profound respiratory depression 6
• Caution should be exercised when prescribing systemic opioids in addition to neuraxial morphine as this can compound the risk of respiratory depression 1

Dose Selection Algorithm

1. For single-shot administration in surgical settings:

   • Start with 0.075-0.1 mg (75-100 μg) for most patients 2, 1
   • Consider lower doses (50 μg) for patients at higher risk of side effects 2
   • Consider higher doses (up to 150 μg) only for patients with anticipated high pain intensity 2

2. For continuous administration in cancer pain:

   • Begin with 0.2-1 mg/day and titrate based on response 3, 4
   • Monitor for dose escalation requirements over time, as patients receiving intrathecal morphine for longer than 2 years often require increases to more than 10 mg/day 4

3. Risk-based adjustments:

   • Reduce doses in elderly patients and those with respiratory compromise
   • Avoid intrathecal morphine in patients with infections, coagulopathy, or very short life expectancy 2

Important Considerations

• Intrathecal morphine appears to have an analgesic efficacy "ceiling," so increasing doses beyond recommendations may increase side effects without improving analgesia 1
• For cancer pain management, consider a trial of intraspinal analgesia using a temporary catheter before implantation of permanent devices 2
• When using intrathecal morphine, implement multimodal analgesia with paracetamol, NSAIDs, and possibly dexamethasone to enhance pain control 2