# Opioid switching and dose conversion in adults with cancer pain

Source: https://onco.cc/protocols/opioid-switching-and-conversion/  
OnCo record `opioid-switching-and-conversion` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Sometimes a strong painkiller has to be changed for another, or given a different way, for example by injection under the skin when swallowing becomes hard. Doses do not swap one for one, so the team works out the new dose from the total taken over 24 hours, often starts a little lower to be safe, and checks closely in the first days.

## Summary

Switching is considered when pain stays uncontrolled despite an appropriate dose, when side effects are unacceptable (Australian guideline 2025, citing ESMO, NCCN, NICE and ASCO; NICE CG140 1.1.25 for persistent central nervous system effects with uncontrolled pain), or when the oral route is lost. WHO (2018) makes no recommendation for or against switching because no randomised trial has tested it, and presents its conversion tables only as examples. The conversion is done on the total 24-hour dose, looked up in a recognised table or calculator. Ratios in the WHO annex (from the Palliative Care Formulary) include oral to subcutaneous morphine 2:1 and oral morphine to subcutaneous hydromorphone 10:1; oral oxycodone is listed at 1.5 times morphine (manufacturer 2). WHO advises reducing the calculated dose of the new opioid by about 50% when switching at high doses, in older or frail people, because of intolerable side effects such as delirium, or after a rapid recent escalation; the Australian guideline says a dose lower than the equivalent should be used when changing drug. The 2025 MASCC-ASCO-AAHPM-HPNA-NICSO guideline, the first international consensus guideline on conversion, reached agreement on 58 of 84 statements and is described in a 2026 review as challenging traditional dose-reduction protocols; it could be read only as an abstract. Methadone is converted by specialists only.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: opioid rotation; opioid conversion; opioid switch; equianalgesic dose; converting oral morphine to subcutaneous; morphine to fentanyl patch conversion; opioid conversion ratio

## Connected records

- protocols: [Strong opioids for cancer pain: starting, titrating, rescue doses and preventing constipation](https://onco.cc/protocols/strong-opioids-for-cancer-pain/), [Syringe driver (syringe pump): setting up and checking a continuous subcutaneous infusion in palliative care](https://onco.cc/protocols/syringe-driver-continuous-subcutaneous-infusion/)
- technologies: [Cancer pain management](https://onco.cc/technologies/pain-management/), [Syringe pumps and subcutaneous syringe drivers](https://onco.cc/technologies/syringe-drivers/)
- drugs: [Fentanyl (transmucosal, for breakthrough cancer pain)](https://onco.cc/drugs/fentanyl/)

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