No, You Cannot Administer Extended-Release Morphine Intravenously
Extended-release (ER) morphine formulations are designed exclusively for oral administration and must never be given intravenously—doing so would deliver the entire extended-release dose immediately, causing potentially fatal respiratory depression and overdose. 1
Understanding the Fundamental Problem
Extended-release morphine products contain polymer-coated pellets or matrix formulations designed to release morphine slowly over 12-24 hours when taken orally. 1 The formulation technology that provides sustained plasma levels with minimal fluctuation is completely incompatible with IV administration. 1
What You Should Use Instead for IV Administration
For Intermittent IV Dosing Every 4 Hours (Not Every 6 Hours)
- Immediate-release morphine should be administered IV every 4 hours, not every 6 hours, as the duration of action of IV morphine is approximately 4 hours. 2, 3, 4
- Peak effects occur within 15-30 minutes after IV administration. 3, 4
- The standard dosing interval for intermittent IV morphine is every 4 hours based on its pharmacokinetic profile. 2, 3
Dosing Conversion from Oral to IV
- The oral to IV morphine ratio is 1:2 to 1:3 (meaning IV morphine is 2-3 times more potent than oral). 4, 5
- If converting from oral extended-release morphine to IV immediate-release morphine: calculate the total daily oral dose, divide by 2-3 to get the IV equivalent, then divide by 6 to get the every-4-hour dose. 4
For Breakthrough Pain Management
- IV rescue doses can be given every 15-30 minutes during titration. 4
- For established patients, an appropriate IV rescue dose is one-fifth of the total daily oral morphine dose converted to IV equivalents. 6
- This approach has been shown safe and effective, with pain reduction within a mean of 17.7 minutes. 6
Critical Safety Considerations
Why Every 4 Hours, Not Every 6 Hours?
- Morphine does not need to be given more frequently than every 4 hours, and extending the interval to 6 hours risks inadequate pain control between doses given morphine's 4-hour duration of action. 2, 3
- Increasing the dose to maintain a 6-hour interval would result in excessive peak concentrations and increased adverse effects without improving overall analgesia. 2
Monitoring Requirements
- A 10 mg IV bolus dose causes only slight increases in PaCO2 (from 4.8 to 5.2 kPa at 5 minutes) when given to patients with moderate pain, indicating good tolerability. 7
- Common adverse effects include nausea, vomiting, and sedation, which are dose-related. 6
- Approximately 6% of patients discontinue morphine due to intolerable adverse effects. 8
Common Pitfalls to Avoid
- Never attempt to crush, dissolve, or inject extended-release formulations—this destroys the controlled-release mechanism and delivers a potentially lethal dose immediately. 1
- Do not extend IV morphine dosing intervals beyond 4 hours based on convenience—this compromises pain control. 2
- Do not use buccal, sublingual, or nebulized routes as absorption is unpredictable with no clinical advantage. 3