What is the recommended dose and duration of morphine (opioid analgesic) for labor pain management?

Morphine Dosing and Duration in Labour

For labor pain management, morphine is not recommended as a first-line agent due to its limited efficacy and significant side effects; instead, non-opioid analgesics should be used first, with neuraxial techniques preferred when available. 1

Recommended Pain Management Algorithm for Labor

First-line options (non-opioid):

• Nonpharmacologic approaches:

  • Ice packs, heating pads to perineum
  • Water immersion/water birth (95% satisfaction rate) 2
  • Relaxation techniques, massage
  • Transcutaneous electrical nerve stimulation (TENS)

• Basic pharmacologic options:

  • Acetaminophen: 975 mg every 8 hours or 650 mg every 6 hours
  • Ibuprofen: 600 mg every 6 hours (after delivery)

Second-line options (if first-line inadequate):

• Neuraxial analgesia (most effective for labor pain):
  • Intrathecal morphine 50-100 μg (low dose preferred to minimize side effects) 1
  • Epidural morphine 2-3 mg if epidural catheter is in place 1

Third-line options (if neuraxial contraindicated/unavailable):

• Systemic opioids as rescue medication only:
  • Morphine IV: 0.1-0.2 mg/kg every 4 hours as needed 3
  • Limited to short-term use due to significant side effects

Important Considerations for Morphine Use

Timing and Duration

• Morphine should be used for the shortest duration possible
• After vaginal delivery, median time to opioid cessation is 0 days (IQR 0-2) 1
• For cesarean delivery, limit to 5-10 tablets of low-dose opioids for severe pain only 1

Side Effects and Risks

• Maternal risks: respiratory depression, nausea, vomiting, dizziness, sedation, constipation 3
• Neonatal risks: respiratory depression if administered close to delivery
• Risk of persistent opioid use: approximately 1 in 300 women exposed to opioids after cesarean delivery develop chronic use 1

Monitoring Requirements

• Respiratory monitoring is essential when using parenteral opioids
• Continuous monitoring for 24 hours after neuraxial morphine administration 1

Special Considerations

Vaginal Delivery

• Pain is generally mild-to-moderate and of limited duration
• Severe pain after vaginal delivery is unusual and should prompt evaluation for complications 1
• Non-opioid analgesics should be sufficient in most cases

Cesarean Delivery

• Basic analgesia should consist of paracetamol and NSAIDs started intraoperatively (after delivery) 1, 4
• Intrathecal morphine (50-100 μg) is recommended if spinal anesthesia is used 1, 4
• Local anesthetic techniques (TAP blocks, wound infiltration) should be considered if intrathecal morphine is not used 1, 4

Pitfalls to Avoid

1. Overprescribing: Prescribing large quantities of opioids increases risk of leftover medication available for diversion or misuse 1

2. Inadequate monitoring: Failure to monitor respiratory status after opioid administration can lead to respiratory depression 3

3. Neglecting basic analgesics: Regular administration of acetaminophen and NSAIDs is essential to limit the need for opioids 1

4. High-dose intrathecal morphine: Doses >100 μg increase side effects without improving analgesia 1

5. Ignoring risk factors for persistent use: Young age, smoking, chronic pain conditions, and use of antidepressants or benzodiazepines increase risk of persistent opioid use 1

In conclusion, morphine should be used judiciously for labor pain, with preference given to non-opioid and neuraxial techniques. When morphine is necessary, use the lowest effective dose for the shortest duration possible to minimize adverse effects and the risk of persistent use.