What is the recommended dose of morphine (opioid analgesic) for managing rigors?

Morphine Dosing for Rigors

For rigors, intravenous morphine should be administered at an initial dose of 1.5 mg IV bolus every 10 minutes until rigors resolve or adverse effects occur. 1

Intravenous Morphine Administration Protocol

• Initial dose: 1.5 mg IV bolus 1
• Frequency: Every 10 minutes until relief of rigors or adverse effects occur 1
• Median effective dose: 4.5 mg (range 1.5-34.5 mg) based on clinical trials 1
• Maximum dose: No absolute upper limit; dose should be titrated to effect 1

Alternative Routes of Administration

• Subcutaneous administration is an acceptable alternative when IV access is unavailable 1, 2
  • Initial dose: Similar to IV but given at 30-minute intervals 2
  • Higher total doses may be required (mean 57.9 mg subcutaneously vs 18.5 mg intravenously) 2
• Oral administration is less effective for acute rigors due to slower onset of action 1
  • If oral route is necessary, immediate-release morphine at 5-10 mg can be used 1

Monitoring During Administration

• Respiratory rate and sedation level should be monitored during titration 1, 3
• Oxygen saturation monitoring is recommended, especially in opioid-naïve patients 3
• Vital signs should be checked after each bolus during the titration phase 3, 4

Potential Adverse Effects

• Respiratory depression is the most serious potential adverse effect 3
• Other common side effects include:
  • Sedation (occurs in up to 60% of patients) 5
  • Nausea and vomiting (occurs in up to two-thirds of patients initially) 1
  • Hypotension, particularly in ambulatory patients 3
  • CNS effects including drowsiness, dizziness, and mental clouding 1

Special Considerations

• Elderly patients can safely receive the same titration protocol as younger patients, with no significant differences in adverse effects 5
• In patients with renal impairment, all opioids should be used with caution and at reduced doses 1
• For patients with chronic kidney disease (stages 4-5), buprenorphine is the safest opioid choice 1
• For patients with inadequate response to morphine, consider opioid rotation to hydromorphone, oxycodone, or fentanyl 6

Important Caveats

• Rapid IV administration may result in chest wall rigidity 3
• Concomitant use of CNS depressants increases risk of respiratory depression 3
• Naloxone should be readily available for reversal of severe opioid-related adverse effects 1
• For patients requiring ongoing treatment, transition to a maintenance regimen with slow-release formulations after the acute phase 1