IV Morphine Dose to Replace 52 mcg/day Morphine Pump
The patient requires approximately 0.017 mg (17 mcg) of IV morphine per day, which translates to roughly 0.7 mcg per hour as a continuous infusion, or approximately 0.002 mg (2 mcg) every 4 hours if given intermittently.
Conversion Calculation
The conversion from intrathecal/epidural morphine (pump) to IV morphine requires understanding the dramatic potency difference between these routes:
Intrathecal morphine is approximately 100-300 times more potent than IV morphine due to direct spinal cord delivery bypassing systemic circulation 1
Using a conservative conversion ratio of 1:100 (intrathecal to IV), 52 mcg/day intrathecal morphine equals approximately 5.2 mg/day IV morphine 1
Using a more aggressive ratio of 1:300, this would equal approximately 15.6 mg/day IV morphine 1
Recommended Starting Approach
Start with the lower end of the conversion range (approximately 5 mg/day IV morphine) and titrate upward based on pain control:
Begin with 0.2 mg IV morphine per hour as a continuous infusion (approximately 5 mg/day) 1, 2
Alternatively, give 1 mg IV morphine every 4 hours as scheduled doses 2
Provide breakthrough doses of 1 mg IV morphine every 15 minutes as needed for inadequate pain control 3
Titration Strategy
If pain control is inadequate after 24 hours, increase the total daily dose by 25-50% to achieve adequate analgesia 1
If the patient requires two or more breakthrough doses within an hour, double the continuous infusion rate 3
Monitor closely for both efficacy and adverse effects, particularly respiratory depression, sedation, nausea, and constipation 1, 2
Critical Safety Considerations
The conversion from intrathecal to IV morphine carries significant risk of both under-dosing (inadequate pain control) and over-dosing (respiratory depression):
Patients previously on intrathecal opioids are opioid-tolerant but may experience withdrawal if under-dosed 1
The wide conversion ratio range (1:100 to 1:300) reflects significant inter-patient variability in response 1
Close monitoring for at least 24-48 hours is essential after initiating IV morphine replacement 2
Have naloxone readily available for reversal of respiratory depression 4
Common Pitfalls to Avoid
Do not use standard oral-to-IV conversion ratios (typically 3:1), as this patient was receiving intrathecal morphine, not oral 5
Do not assume linear dose equivalence - incomplete cross-tolerance between routes may require dose adjustments 5, 6
Do not delay breakthrough dosing - pain exacerbations should be treated promptly with IV boluses every 15 minutes as needed 3, 2
The 52 mcg/day intrathecal dose is relatively low, suggesting either good baseline pain control or recent pump initiation, which should inform your starting IV dose selection 7