Equianalgesic dosing of opioids Opioid medications have differing potencies. When converting from one opioid medication to another, it is critical to understand the equivalent analgesic (equianalgesic) dose to ensure continued efficacy without untoward side effects (see Table 10). The dose, administration route, and therapy duration must be considered. Multiple opioid conversion charts are
available. Clinicians must consider individual patient factors and the characteristics of the opioid medications and delivery systems when converting between opioid products. Closely monitor patients following conversion for efficacy and potential adverse effects.
Table 10. Opioid Equianalgesic Table (Stanford College of Medicine, 2022) Medication Approximate Equianalgesic Oral Dose
Approximate Equianalgesic Intravenous Dose
Conversion Factor to Oral Morphine Parenteral morphine is 3 times as potent as oral morphine. Oral oxycodone is roughly 1.5 times more potent than oral morphine. Oral hydrocodone is roughly 1.5 times more potent than oral morphine. Oral hydromorphone is about 4 to 7 times as potent as oral morphine. Parenteral hydromorphone is 20 times as potent as oral morphine. Transdermal fentanyl is ~80 times as potent as oral morphine. (See Table 5 to convert morphine to fentanyl transdermal patches.)
Morphine
30 mg
10 mg
Oxycodone
20 mg
Hydrocodone
20 to 30 mg
Hydromorphone
7 mg
1.5 mg
Fentanyl
100 mcg (0.1 mg) 15 mcg/hour
Methadone
Variable
Variable
Tramadol
300 mg
0.1
Medication
Approximate Equianalgesic Oral Dose
Approximate Equianalgesic Intravenous Dose
Conversion Factor to Oral Morphine
Codeine
200 mg
0.15
Oral morphine is about 10 times more potent than oral meperidine and about twice as potent as parenteral meperidine (mg for mg).
Meperidine
300 mg of oral meperidine
75 mg of parenteral meperidine
*Note: To convert to ER/LA opioids, see conversion factors listed in Table 5. Calculation of equianalgesic dosages Follow these three steps to calculate equianalgesic dosages when changing to a different opioid analgesic: Step 1: Calculate the total daily dose of the current opioid. Step 2: Determine the equianalgesic dose using the appropriate conversion factor or ratio. Clinical case example CD is a 32-year-old female with chronic pain. She is taking Exalgo 16 mg once daily and hydromorphone immediate-release 4 mg three times daily for breakthrough pain. The patient should be transitioned to MS Contin due to insurance issues. What dose of MS Contin should be started? Step 1: Calculate the total daily dose of the current opioid. Exalgo 16 mg once daily + hydromorphone immediate-release 4 mg three times daily = 28 mg/day hydromorphone Step 2: Determine the equianalgesic dose using the appropriate conversion factor or ratio.
Step 3: Reduce the new opioid analgesic dose by 33% to 50% to account for cross-tolerance, dosing ratio variation, and patient variability. Determine a new regimen based on the available dosage form(s) of the new opioid.
Oral hydromorphone to oral morphine conversion ratio: 4 28 mg hydromorphone/day × 4 = 112 mg morphine/day OR 28 mg hydromorphone = equianalgesic dose of morphine 7.5 mg 30 mg Equianalgesic dose of morphine/day = 112 mg Step 3: Reduce dose by 33% to 50% to account for cross- tolerance; determine a new regimen based on available dosage forms of the new opioid.
Total daily dose of morphine = 74 to 56 mg/day New regimen: MS Contin 30 mg every 12 hours (Total morphine dose = 60 mg/day)
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