Morphine to Oxycodone: how to convert safely

Bottom line

Worked example

1. Total the 24-hour morphine dose — say 30 mg/day oral.
2. Convert to morphine equivalents: 30 mg × 1 = 30 mg MME/day.
3. Convert to oxycodone: 30 ÷ 1.5 = 20 mg/day.
4. Apply a 25–50% cross-tolerance reduction: start near 15 mg/day or lower, divided by the dosing interval, with breakthrough doses available.

Try it with your patient's numbers

Cautions specific to this switch

• Active metabolites (M3G/M6G) accumulate in renal impairment — avoid or dose-reduce morphine when eGFR is reduced, and consider an alternative agent in dialysis patients.
• Histamine release can cause pruritus and hypotension, which is not a true allergy but is often documented as one.
• Oxycodone is metabolized by CYP3A4 and CYP2D6 — strong CYP3A4 inhibitors (azoles, clarithromycin, some antivirals) can raise levels substantially.
• No parenteral form is available in the US; if the patient will lose enteral access, plan the rotation to an IV-capable agent before it happens.
• Equianalgesic tables are population averages. Re-assess pain, sedation (e.g. POSS), and respiratory status within hours of the first converted dose, not days.

Frequently asked questions

How much oxycodone equals 30 mg of oral morphine per day?

30 mg/day of oral morphine is approximately 20 mg/day of oral oxycodone (30 mg × 1 MME factor ÷ 1.5 = 20 mg), before any cross-tolerance reduction. Most patients switching opioids should start 25–50% below the calculated equianalgesic dose.

What is the conversion factor from morphine to oxycodone?

Oral morphine has a morphine milligram equivalent (MME) factor of 1 and oral oxycodone a factor of 1.5, so 1 mg of morphine ≈ 0.7 mg of oxycodone. Equianalgesic tables are population averages — individual response varies, so titrate to effect.

Why reduce the dose for incomplete cross-tolerance?

Tolerance to one opioid does not fully transfer to another. When rotating from morphine to oxycodone, standard practice is to reduce the calculated equianalgesic dose by 25–50% and provide breakthrough doses while re-titrating. Frail or elderly patients warrant the larger reduction.

Is this conversion exact?

No. Published equianalgesic factors are averages with wide interpatient variability, and they differ slightly between references. Treat the calculated dose as a starting estimate, apply a cross-tolerance reduction, and reassess pain and sedation frequently after the switch.