Oxycodone Equivalent for 15 mg Oral Morphine
For 15 mg oral morphine, the equivalent oxycodone dose is 10 mg.
Conversion Ratio
The standard equianalgesic conversion between oral morphine and oral oxycodone is 1.5:1 (morphine:oxycodone), meaning 15 mg oral morphine equals 10 mg oral oxycodone 1. This ratio is endorsed by the Centers for Disease Control and Prevention and represents the most widely accepted conversion factor in clinical practice 1.
Clinical Context and Application
- This 1.5:1 ratio is supported by multiple research studies demonstrating that 1 mg oxycodone provides similar analgesic efficacy to approximately 1.5 mg morphine 2.
- The conversion is straightforward for this calculation: 15 mg morphine ÷ 1.5 = 10 mg oxycodone 1.
- This dose (10 mg oxycodone) falls within the recommended initial dosing range for opioid-naïve patients, which is 5-15 mg oral morphine equivalent 3.
Important Caveats for Opioid Rotation
If you are switching a patient already taking morphine to oxycodone (opioid rotation), rather than simply calculating an equivalent dose, you must reduce the calculated equianalgesic dose by 25-50% to account for incomplete cross-tolerance 1, 4. This would mean:
- Calculate the equivalent: 10 mg oxycodone
- Then reduce by 25-50%: start with 5-7.5 mg oxycodone
- This reduction applies only to opioid rotation, not to simple dose equivalency calculations 1
Pharmacologic Considerations
- Oxycodone has higher oral bioavailability (60-87%) compared to morphine, which contributes to its greater potency per milligram 5.
- Both medications are short-acting opioid agonists that can be easily titrated, making them preferred choices for pain management 3.
- Morphine should be used with caution in renal insufficiency due to accumulation of morphine-6-glucuronide, whereas oxycodone undergoes hepatic metabolism via cytochrome P450 3, 5.