What is the equivalent dose of liquid morphine (morphine) for a patient taking morphine Extended Release (ER) 30 mg?

Converting Morphine ER 30 mg to Liquid Morphine

For a patient taking morphine ER 30 mg, convert to liquid morphine (immediate-release) 15 mg every 4 hours, which equals 90 mg total daily dose.

Conversion Algorithm

Step 1: Calculate Total Daily Morphine Dose

• Morphine ER 30 mg is typically dosed every 12 hours (twice daily) 1
• Total daily dose = 30 mg × 2 = 60 mg per day 1

Step 2: Determine Immediate-Release Dosing Schedule

• Liquid morphine (immediate-release) should be dosed every 4 hours for around-the-clock pain control 1, 2
• This equals 6 doses per 24-hour period 1

Step 3: Calculate Individual Dose

• Divide total daily dose by number of doses: 60 mg ÷ 6 doses = 10 mg every 4 hours 1
• Alternatively, if converting from extended-release to immediate-release formulations, the same total daily dose applies with a 1:1 ratio 3, 2

Step 4: Add Breakthrough Dose

• Prescribe additional liquid morphine for breakthrough pain equal to the 4-hourly dose (10 mg in this case) 1
• This can be given as frequently as every 1-2 hours if needed during titration 1

Important Clinical Considerations

Bioequivalence Between Formulations

• Oral morphine immediate-release (liquid) and extended-release formulations are bioequivalent on a milligram-per-milligram basis when comparing total daily doses 4, 2, 5
• The oral-to-oral conversion ratio is 1:1 3, 2

Dosing Flexibility

• A double dose at bedtime (20 mg) can be given to avoid nighttime awakening, reducing the schedule to 5 doses daily 1
• Some patients may require dosing every 3 hours rather than 4 hours due to individual pharmacokinetics 6

Titration Guidance

• If pain returns before the next scheduled dose, increase the regular dose rather than increasing frequency 1
• Most patients achieve adequate analgesia with doses between 100-250 mg daily, though the range extends from 25 mg to 2000 mg daily 2
• Approximately 96% of patients achieve "no worse than mild pain" with appropriate morphine titration 2

Critical Pitfalls to Avoid

Common Errors

• Do not confuse oral-to-oral conversion (1:1) with oral-to-parenteral conversion (3:1) 3
• Do not use modified-release morphine for breakthrough pain—only immediate-release formulations should be used for rescue dosing 1
• Do not increase dosing frequency beyond every 4 hours for scheduled doses—instead increase the individual dose 1

Mandatory Concurrent Prescriptions

• Always prescribe a stimulant laxative (senna/docusate) prophylactically with initiation of opioid therapy 1, 6
• Increase laxative dose when escalating opioid dose 1, 6
• Approximately 6% of patients discontinue morphine due to intolerable adverse effects, most commonly constipation 2

Monitoring Requirements

• Reassess pain control within 24-48 hours of conversion 1
• Maintain adequate hydration and dietary fiber 1, 6
• Monitor for excessive sedation, particularly in the first 48 hours after conversion 7