What is the recommended dosing for rotating a patient from MS‑Contin (morphine sulfate controlled‑release) 30 mg twice daily to OxyContin (oxycodone controlled‑release)?

Opioid Rotation from MS Contin 30mg BID to OxyContin

For a patient on MS Contin 30mg twice daily (total 60mg/day oral morphine), rotate to OxyContin 30mg daily given as 15mg twice daily, which represents a 25% dose reduction from the calculated equianalgesic dose to account for incomplete cross-tolerance. 1

Step-by-Step Conversion Protocol

Calculate Total Daily Morphine Dose

• Current regimen: MS Contin 30mg BID = 60mg oral morphine per day 1

Apply Equianalgesic Conversion Ratio

• Oral morphine to oral oxycodone ratio is 2:1 (morphine is half as potent as oxycodone) 2, 3
• Calculated equianalgesic dose: 60mg morphine ÷ 2 = 30mg oxycodone per day 2

Reduce for Incomplete Cross-Tolerance

• Reduce the calculated equianalgesic dose by 25-50% when rotating between opioids 1, 2
• For well-controlled pain with minimal side effects, use a 25% reduction 1
• For poorly controlled pain or significant side effects, use a 50% reduction 1
• Recommended starting dose: 30mg oxycodone × 0.75 (25% reduction) = 22.5mg daily, rounded to 20-30mg daily 1

Prescribe OxyContin Regimen

• OxyContin 10mg twice daily (20mg total) to 15mg twice daily (30mg total) is the appropriate starting range 1, 4
• The 25% reduction (30mg daily) is preferred if pain is currently well-controlled 1
• The 50% reduction (15mg daily as 10mg BID) is preferred if there are significant opioid side effects or concerns about tolerance 1

Breakthrough Medication Requirements

Prescribe immediate-release oxycodone at 10-20% of the total 24-hour dose for breakthrough pain, available every 4 hours as needed. 1, 5

• For OxyContin 15mg BID (30mg total daily): breakthrough dose = 3-6mg immediate-release oxycodone every 4 hours PRN 1
• For OxyContin 10mg BID (20mg total daily): breakthrough dose = 2-4mg immediate-release oxycodone every 4 hours PRN 1
• If more than 3-4 breakthrough doses are required per day, increase the scheduled OxyContin dose by 25-50% 1, 2

Titration and Monitoring Protocol

Initial 24-48 Hour Period

• Monitor closely for inadequate pain control and opioid-related adverse effects during the first 24-48 hours 1
• Titrate liberally and rapidly to analgesic effect if pain remains severe or inadequately controlled 1
• Review total daily opioid consumption (scheduled plus breakthrough doses) every 24 hours 5

Dose Adjustments

• Increase the baseline OxyContin dose based on total breakthrough medication usage 1, 5
• Add the total daily breakthrough oxycodone to the scheduled dose, then redistribute as twice-daily dosing 5
• Example: If patient uses 30mg OxyContin daily plus 12mg breakthrough oxycodone, increase to OxyContin 21mg BID (42mg total daily) 5

Steady State Considerations

• Steady state is achieved in approximately 24 hours for OxyContin (5 half-lives of oxycodone's 3-5 hour half-life) 1, 3
• Reassess pain control and side effects at 24 hours, 48 hours, and 5-7 days 1

Critical Safety Considerations

Prophylactic Bowel Regimen

• Institute stimulant laxative (senna) plus stool softener (docusate) prophylactically at initiation 2, 1
• Start with senna/docusate 2 tablets every morning, maximum 8-12 tablets per day 2
• Constipation does NOT improve over time with opioids and requires ongoing management 2

Monitoring for Adverse Effects

• Common side effects include nausea, constipation, drowsiness, vomiting, pruritus, and dizziness 3
• Oxycodone causes somewhat less nausea, hallucinations, and pruritus than morphine 3
• Most side effects (except constipation) improve within days to weeks 2, 1

Special Population Considerations

• No dose reduction needed in elderly patients or those with moderate hepatic or renal failure 3
• However, avoid morphine (not oxycodone) in patients with renal disease due to accumulation of morphine-6-glucuronide 2, 1

Common Pitfalls to Avoid

Do Not Skip the Dose Reduction

• Never use a 1:1 conversion without dose reduction – this ignores incomplete cross-tolerance and risks opioid toxicity 1
• The 25-50% reduction is mandatory, not optional 1, 2

Do Not Use Extended-Release for Titration Alone

• While controlled-release oxycodone CAN be used for titration (unlike transdermal fentanyl), always provide immediate-release breakthrough medication during the conversion period 2, 1, 6
• Dose adjustments should occur no more frequently than every 24 hours 5

Do Not Forget Tablet Administration Instructions

• OxyContin tablets must be swallowed whole and must not be broken, chewed, or crushed 4, 3
• Breaking or crushing destroys the controlled-release mechanism and can cause rapid release of a potentially fatal dose 4

Do Not Underprescribe Breakthrough Medication

• The breakthrough dose should equal the full 4-hourly equivalent (10-20% of daily dose), not a smaller amount 1, 5
• Underdosing breakthrough medication leads to inadequate pain control and patient suffering 5

When to Consider Alternative Strategies

If Conversion Fails

• If pain remains inadequately controlled after 2-3 dose adjustments, consider rotation to a different opioid (hydromorphone, methadone) or refer to pain specialist 1
• If significant side effects persist despite dose adjustment, consider opioid rotation rather than continuing to escalate 2, 1

Adjuvant Analgesics

• Consider adding gabapentin (300-1200mg TID) or pregabalin (75-300mg BID) for neuropathic pain components 1
• Consider adding duloxetine (30-60mg daily) or nortriptyline (25-100mg nightly) for neuropathic pain 1