What are the morphine equivalents for different opioids, including oxycodone (OxyContin), hydrocodone (Vicodin), hydromorphone (Dilaudid), and fentanyl?

Morphine Equivalents for Common Opioids

The CDC provides standardized conversion factors to calculate morphine milligram equivalents (MME): hydrocodone 1.0, oxycodone 1.5, hydromorphone 5.0, fentanyl transdermal 2.4 (mcg/hr), methadone 4.7, codeine 0.15, tramadol 0.2, tapentadol 0.4, and oxymorphone 3.0. 1

Standard Conversion Factors

To calculate MME, multiply the total daily dose of the opioid by its conversion factor:

• Hydrocodone: 1.0 conversion factor (20 mg daily = 20 MME) 1
• Oxycodone: 1.5 conversion factor (20 mg daily = 30 MME; 30 mg oral oxycodone = 60 mg oral morphine) 2, 1
• Hydromorphone (Dilaudid): 5.0 conversion factor 1
• Fentanyl transdermal: 2.4 conversion factor applied to mcg/hr (75 mcg/hr patch = 180 MME daily) 1
• Methadone: 4.7 conversion factor 1
• Codeine: 0.15 conversion factor 1
• Tramadol: 0.2 conversion factor 1
• Oxymorphone: 3.0 conversion factor 1

Route of Administration Conversions

The conversion ratio for IV/IM morphine to oral morphine is approximately 1:3, meaning parenteral morphine is three times more potent than oral morphine. 1

• 10 mg IV morphine = 30 mg oral morphine 1
• For parenteral administration, use one-third of the oral dose 3
• IV fentanyl to IV morphine conversion is 100:1 (100 mcg IV fentanyl = 10 mg IV morphine) 1
• For continuous parenteral fentanyl infusion to transdermal fentanyl, use a 1:1 ratio (mcg of parenteral fentanyl equals mcg/hr of transdermal fentanyl) 4

Critical Safety Warnings and Dose Reduction Requirements

When converting between opioids, reduce the calculated equianalgesic dose by 25-50% to avoid overdose from incomplete cross-tolerance. 1, 5

• Conversion factors are estimates only and cannot account for individual variability in genetics and pharmacokinetics 1
• The new opioid should typically be dosed 25-50% lower than the calculated equianalgesic dose 1, 5
• This dose reduction is essential because cross-tolerance between opioids is incomplete 1

Common Pitfalls to Avoid

Confusing mcg/hr with mg/day for fentanyl patches is a potentially fatal error. 1

• Always verify units when calculating fentanyl conversions 1
• Failing to reduce the calculated dose by 25-50% when rotating opioids can cause overdose 1
• Fentanyl patches take 12-24 hours to reach therapeutic levels, requiring continuation of the previous opioid during this initial period 4

Clinical Dosing Thresholds

The CDC defines opioid dose categories as:

• Low dose: up to 40 MME/day 1, 5
• Moderate dose: 41-90 MME/day 1, 5
• High dose: ≥91 MME/day 1, 5

Pause and carefully reassess individual benefits and risks before increasing total opioid dosage to ≥50 MME/day. 1

Special Considerations for Specific Opioids

Morphine

• Initial oral dose for opioid-naïve patients: 5-15 mg of short-acting morphine 3
• Initial IV dose for opioid-naïve patients: 2-5 mg 3
• Use with caution in renal insufficiency due to accumulation of morphine-6-glucuronide, which can cause neurologic toxicity 3, 2

Fentanyl

• 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 3
• Patches are typically changed every 72 hours, though some patients may require replacement every 48 hours 4
• Avoid application of heat (fever, heating pads, electric blankets) as this accelerates fentanyl absorption 4

Hydrocodone

• May be approximately equipotent with oral morphine, but equivalence data are not well substantiated 3
• Available only in combination with acetaminophen or ibuprofen, requiring monitoring for safe limits 3

Methadone

• Should be started only by clinicians with specific training in its risks and uses due to long half-life (8 to >120 hours) and high interindividual variability 3, 5
• Obtain an electrocardiogram prior to initiation, at 30 days, and yearly thereafter 5