Opioid dose conversion and route switching
A stepwise method for converting between opioids and routes using ANZCA oral morphine equivalents, why oral to parenteral ratios differ between drugs, incomplete cross-tolerance, breakthrough dosing, and the timing of fentanyl patch and subcutaneous infusion switches, with worked examples.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Convert in steps: total 24-hour dose → oMEDD → new opioid and route → reduce for cross-tolerance → set breakthrough dose → review.
- ANZCA factors (October 2025): oral oxycodone 1.5, hydromorphone 5, tapentadol 0.3, tramadol 0.2, codeine 0.13; parenteral morphine 3, oxycodone 3, hydromorphone 15; fentanyl patch 3 per mcg/h, buprenorphine patch 2 per mcg/h.
- Reduce by 25 to 50% when switching to a different opioid. Don't reduce for a route change of the same drug.
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Sources
- PS01(PM) Appendix 2: Opioid dose equivalenceAU/NZFaculty of Pain Medicine, ANZCA, October 2025
- Therapeutic Guidelines: Palliative CareAU/NZTherapeutic Guidelines Limited, 2024
- Australian Medicines HandbookAU/NZAustralian Medicines Handbook Pty Ltd, 2026
- Conversion ratios for opioid switching in the treatment of cancer pain: a systematic reviewPalliat Med (Mercadante and Caraceni, 2011;25:504-15), 2011
- Last updated
- 14 November 2026
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