What is the recommended dosing for morphine (opioid) intravenous (IV) administration for palliative care?

IV Morphine Dosing in Palliative Care

For intravenous morphine administration in palliative care, the recommended starting dose is 0.1 mg to 0.2 mg per kg every 4 hours as needed for pain management, with dose adjustments based on pain severity, adverse events, and patient factors. 1

Initial Dosing and Titration

• For opioid-naïve patients with severe pain requiring rapid titration, administer 1.5 mg IV boluses every 10 minutes until pain relief is achieved (or adverse effects occur) 2
• This IV titration approach has been shown to achieve satisfactory pain relief in 84% of patients within 1 hour compared to only 25% with oral immediate-release morphine 2
• For patients already receiving opioids, calculate the 24-hour analgesic requirement of their current regimen before converting to IV morphine 2
• The relative potency ratio of oral to IV morphine in patients receiving chronic treatment for cancer pain is 3:1 (i.e., 30 mg oral morphine = 10 mg IV morphine) 2, 3

Continuous Infusion Guidelines

• After initial titration with bolus doses, a continuous infusion may be initiated based on the total amount of morphine required during titration 4
• The mean starting rate for continuous IV morphine infusion in palliative care is approximately 3.3 mg/hour (range: 0.4-30.0 mg/hour) 5
• All patients should receive around-the-clock dosing with provision of breakthrough doses to manage transient exacerbations of pain 2
• Breakthrough doses should be approximately 10-15% of the total daily dose 2
• If more than four breakthrough doses per day are necessary, the baseline continuous infusion rate should be adjusted 2

Dose Adjustments

• The regular infusion rate should be adjusted to account for the total amount of breakthrough morphine required 2
• If pain returns consistently before the next regular dose is due, increase the regular dose 2
• The plasma elimination half-life of morphine is 2-4 hours, and steady state is reached within 24 hours after starting treatment or making dose adjustments 2
• Continuous infusion rates may need to be escalated significantly at end of life, with studies showing mean increases of 130% from initiation to time of death 5

Side Effect Management

• Common adverse effects include constipation, nausea, vomiting, drowsiness, cognitive impairment, and respiratory depression 2, 1
• If side effects become problematic, consider:
  • Reducing the opioid dose if possible 2
  • Adding adjuvant medications (antiemetics for nausea, laxatives for constipation) 2
  • Switching to another opioid if side effects persist 2
• For respiratory depression, naloxone is available as a short-acting opioid antagonist for IV use to reverse symptoms of accidental severe opioid overdose 2

Special Considerations

• Avoid using morphine in patients with renal failure due to the risk of accumulation of renally cleared metabolites 2
• For patients with poor peripheral circulation, IV administration may be necessary instead of other routes 2
• Intravenous administration should be done slowly to minimize adverse effects 6
• Daytime drowsiness, dizziness, or mental clouding commonly occur at the start of treatment but typically resolve within a few days as patients stabilize 2

Conversion to Other Opioids

• When converting from IV morphine to IV hydromorphone, use a ratio of 5:1 (10 mg IV morphine = 2 mg IV hydromorphone) 2, 7
• For example, if a patient is taking IV morphine at 8 mg/hour (192 mg/day), this would convert to approximately 2 mg/hour of IV hydromorphone 2
• When converting between opioids, if pain was effectively controlled, reduce the calculated equianalgesic dose by 25-50% to account for incomplete cross-tolerance 2