Opioid Conversion Guidelines

Introduction to Opioid Conversion

The Centers for Disease Control and Prevention (CDC) provides standardized conversion factors to calculate morphine milligram equivalents (MME), with oxycodone using a 1.5 conversion factor, hydrocodone using 1.0, and transdermal fentanyl using 2.4 (mcg/hr) 1

The CDC recommends the following conversion factors: hydrocodone 1.0, oxycodone 1.5, fentanyl transdermal 2.4, hydromorphone 5.0, methadone 4.7, codeine 0.15, tramadol 0.2, tapentadol 0.4, and oxymorphone 3.0 1
These conversion factors should be multiplied by the daily opioid dose to determine MME 1, 2

For hydrocodone, a patient taking 20 mg total daily equals 20 MME daily 1
For oxycodone, 20 mg total daily equals 30 MME daily (20 mg × 1.5 = 30 MME) 1
For transdermal fentanyl, a 75 mcg/hr patch equals 180 MME daily (75 × 2.4 = 180 MME) 1

The CDC warns that these conversion factors are estimates only and cannot account for individual variability in genetics and pharmacokinetics 1, 2
When converting between opioids, the new opioid should typically be dosed 25-50% lower than the calculated equianalgesic dose to avoid overdose from incomplete cross-tolerance 1, 2, 3

The CDC defines opioid dose categories as low dose (up to 40 MME/day), moderate dose (41-90 MME/day), and high dose (≥91 MME/day) 1, 3
Clinicians should pause and carefully reassess individual benefits and risks before increasing total opioid dosage to ≥50 MME/day 1, 2

The conversion ratio for IV/IM morphine to oral morphine is approximately 1:3, meaning 10 mg IV morphine equals 30 mg oral morphine 4
The conversion ratio for IV fentanyl to IV morphine is 100:1, meaning 100 mcg IV fentanyl equals 10 mg IV morphine 4

Confusing mcg/hr with mg/day for fentanyl patches is a potentially fatal error 1, 2
Failing to reduce the calculated dose by 25-50% when rotating opioids can cause overdose due to incomplete cross-tolerance 1, 3, 4

The National Comprehensive Cancer Network recommends an initial oral dose for opioid-naïve patients of 5-15 mg of short-acting morphine, and an initial IV dose of 2-5 mg, with caution in renal insufficiency due to accumulation of morphine-6-glucuronide 5, 6
For parenteral administration, the guideline suggests using one-third of the oral dose, with a conversion ratio for IV/IM morphine to oral morphine of approximately 1:3 5, 6

Transdermal fentanyl is not indicated for rapid opioid titration and should only be used in opioid-tolerant patients after pain is controlled by other opioids, according to the National Comprehensive Cancer Network 6
Hydrocodone may be approximately equipotent with oral morphine, but equivalence data are not well substantiated, and it is available only in combination with acetaminophen or ibuprofen, requiring monitoring for safe limits 6
Methadone should be started only by clinicians with specific training in its risks and uses due to its long half-life and high interindividual variability 6