Opioid Conversion Guidelines

Introduction to Opioid Equivalence

• The CDC Guideline for Prescribing Opioids for Chronic Pain recommends that hydromorphone has a conversion factor of 4 when calculating morphine milligram equivalents (MME) 1
• According to the CDC Guideline, 1 mg of hydromorphone equals 4 mg of morphine in MME terms 1

Clinical Application of Conversion Factors

• The American College of Physicians and other medical societies support the idea that when converting between opioids, these conversion factors help clinicians maintain appropriate analgesic effect while minimizing adverse effects, with the potency of hydromorphone being approximately 5-7 times more potent than morphine 2
• The potency of hydromorphone allows for smaller volume administration, which may be beneficial in certain clinical scenarios, such as patient-controlled analgesia 2

Route-Specific Considerations

• When converting from IV morphine to IV hydromorphone, a ratio of approximately 5:1 is recommended, such as 10 mg IV morphine equals 2 mg IV hydromorphone, as suggested by clinical guidelines 2
• For oral to parenteral hydromorphone conversions, a ratio of approximately 5:1 is supported, with oral hydromorphone having approximately one-fifth the potency of parenteral hydromorphone 3

Common Pitfalls and Caveats

• Conversion ratios are approximate guides, and clinical judgment is essential when converting between opioids, as stated by the CDC and other medical societies 3
• These conversion factors are specifically for calculating MME for comparison purposes and may differ from equianalgesic dosing when switching patients between medications, with the CDC and other medical societies recommending careful consideration of individual patient needs 1, 2
• When converting between opioids, incomplete cross-tolerance should be considered, which may require dose reduction when switching to a new opioid, as recommended by medical societies 2
• Patients should be monitored closely after conversion for both pain control and potential adverse effects, with the goal of optimizing patient outcomes 3

Opioid Conversion Guidelines

Conversion Factors and Calculations

• The National Comprehensive Cancer Network recommends converting IV morphine to oral morphine using a ratio of approximately 1:3, accounting for oral bioavailability, resulting in a dose of 540 mg oral morphine from 180 mg IV morphine 4
• When converting between opioids, it is recommended to reduce the calculated dose by 25-50% to account for incomplete cross-tolerance, resulting in a starting oral morphine dose of 270-405 mg/day 4
• The conversion ratio may vary based on the patient's current opioid tolerance level, and clinical judgment is essential when converting between opioids 4

Dosing and Administration

• After conversion, patients should be monitored closely for both efficacy and side effects, with dose adjustments made as needed 4
• Consider dividing the total daily oral morphine dose into multiple doses (e.g., every 4 hours for immediate release or every 12 hours for extended release) 4

Opioid Conversion from Tylenol #3 to Hydromorphone Contin

Direct Conversion Recommendation

• For a patient taking 8 Tylenol #3 tablets daily, convert to approximately 6-9 mg oral hydromorphone daily, divided into 2 doses of Hydro Morph Contin, with the lower end preferred initially, as recommended by the National Comprehensive Cancer Network 5

Step-by-Step Conversion Algorithm

• Each Tylenol #3 contains 30 mg codeine, and 8 tablets is equivalent to 240 mg codeine per day, according to the National Comprehensive Cancer Network 5
• Using standard equianalgesic ratios, 200 mg oral codeine is approximately equal to 30 mg oral morphine, as stated by the National Comprehensive Cancer Network 5
• The calculated morphine equivalent dose is 36 mg oral morphine equivalent per day, based on the conversion ratio provided by the National Comprehensive Cancer Network 5

Critical Safety Considerations

• Prescribe immediate-release hydromorphone for breakthrough pain at 10-15% of the total daily dose, as recommended by the National Comprehensive Cancer Network 5
• If average pain intensity remains >4/10, increase the total daily dose by 25-50%, according to the National Comprehensive Cancer Network 5

Common Pitfalls to Avoid

• Codeine is a prodrug requiring CYP2D6 metabolism to morphine for analgesic effect, and approximately 10% of patients are poor metabolizers, as noted by the National Comprehensive Cancer Network 6
• Hydromorphone has less problematic metabolite accumulation compared to morphine and codeine, although caution is still warranted in severe renal impairment, as stated by the National Comprehensive Cancer Network 6
• The patient may require additional non-opioid analgesia after conversion, considering the discontinuation of acetaminophen, as suggested by the National Comprehensive Cancer Network 6

Opioid Conversion and Morphine Equivalent Dose Calculation

Basic Calculation Algorithm

• The National Comprehensive Cancer Network recommends calculating the total amount of the current opioid taken in a 24-hour period, including all scheduled doses plus average daily breakthrough medication use, to determine the total daily opioid dose 7, 8
• The total daily opioid dose should be multiplied by its specific conversion factor to morphine, and all converted doses should be summed to obtain the total daily MME, according to the National Comprehensive Cancer Network 7

Conversion Factors

• The National Comprehensive Cancer Network suggests using standard conversion ratios to convert to oral morphine equivalents, including a 1:3 ratio for IV to oral morphine 9
• Oxymorphone can be converted to oral morphine equivalent using a 1:3 ratio, as recommended by the National Comprehensive Cancer Network 7, 10
• Fentanyl transdermal should be converted using manufacturer-specific tables, as recommended by the National Comprehensive Cancer Network 7, 10, 11

Special Considerations

• The National Comprehensive Cancer Network recommends using unique, dose-dependent conversion ratios for methadone, with a variable ratio based on the specific dose of oral morphine 7, 10
• Methadone's potency relative to morphine increases with higher baseline morphine doses, according to the National Comprehensive Cancer Network 7, 10

Critical Considerations for Patient-Specific Factors

• The National Comprehensive Cancer Network suggests that MME calculations remain the same in patients with renal impairment, but actual dosing must be reduced 9
• Morphine, hydromorphone, hydrocodone, oxymorphone, and codeine should be used with caution in patients with renal impairment due to accumulation of active metabolites, as recommended by the National Comprehensive Cancer Network 9

Common Pitfalls to Avoid

• The National Comprehensive Cancer Network recommends avoiding critical errors in calculation, such as using the same conversion ratios when converting from methadone to other opioids 7, 10
• MME calculations are for comparison purposes only, and when switching patients between opioids, the calculated equianalgesic dose should be reduced by 25-50% to account for incomplete cross-tolerance, according to the National Comprehensive Cancer Network 7, 8, 10
• All patients require close monitoring after any opioid conversion, regardless of calculated MME, as recommended by the National Comprehensive Cancer Network 9

Opioid Equianalgesic Dosing Guidelines (National Comprehensive Cancer Network)

Standard Equianalgesic Conversion Ratios

• The NCCN recommends that for opioid‑naïve adults with normal organ function, oral morphine 30 mg is equivalent to oral hydromorphone 6 mg, IV morphine 10 mg, and IV hydromorphone 1.5 mg. [12][13]
• Oral morphine 30 mg is the reference point for other oral opioids:
  
  • Oral hydromorphone 6 mg (5 : 1 ratio to morphine) 12
  • Oral oxycodone ≈ 20 mg 13
  • Oral hydrocodone ≈ 30 mg 13
  • Oral codeine 200 mg 12
• Parenteral equivalents:
  
  • IV morphine 10 mg (oral‑to‑IV ratio 3 : 1) [12][13]
  • IV hydromorphone 1.5 mg (oral‑to‑IV ≈ 5 : 1; IV morphine‑to‑IV hydromorphone 5‑7 : 1) [12][13]
  • IV fentanyl 0.1 mg (100 µg) [12][13]

Dose‑Reduction Rules When Switching Opioids

• When pain is well‑controlled, calculate the equianalgesic dose of the new opioid and reduce it by 25‑50 % to account for incomplete cross‑tolerance [12][13].
• When pain is poorly controlled, the calculated dose may be used unchanged (100 %) or increased by up to 25 % [12][13].
• The reduction is mandatory because different opioids exhibit incomplete cross‑tolerance, making patients more sensitive to the new agent [12][13].

Methadone‑Specific Guidance

• Methadone conversion is dose‑dependent and non‑linear; higher baseline morphine doses make methadone relatively more potent [14][15].
• For patients on oral morphine 100‑300 mg/day, use an approximate 8 : 1 morphine‑to‑methadone ratio 14.
• For oral morphine > 300 mg/day, ratios may reach 12 : 1 or higher [14][15].
• Never apply morphine‑to‑methadone ratios in reverse when converting from methadone to another opioid 15.
• When discontinuing methadone, start with a conservative 1 : 1 oral methadone‑to‑oral morphine dose on day 1 and supplement with short‑acting opioids as needed 15.

Renal Impairment Considerations

• Avoid morphine and codeine entirely in patients with creatinine clearance < 30 mL/min because of accumulation of toxic metabolites (morphine‑3‑glucuronide, morphine‑6‑glucuronide, norcodeine) [12][13].

Breakthrough Pain Dosing

• Prescribe a breakthrough dose equal to 10‑20 % of the total 24‑hour opioid dose, available every 1‑4 hours as needed [12][13].
• Use the same opioid for breakthrough dosing as for the scheduled regimen whenever possible 12.
• If a patient requires more than 3‑4 breakthrough doses per day, increase the scheduled baseline dose by 25‑50 % 12.
• Transmucosal fentanyl (lozenge, buccal tablet, sublingual film) is restricted to opioid‑tolerant patients (≥ 60 mg oral morphine equivalents daily for ≥ 1 week) 12; start with the lowest available dose (100‑200 µg) and titrate because no reliable equianalgesic conversion exists [12][13].

Transdermal Fentanyl Conversion

• Do not use IV fentanyl conversion ratios for transdermal patches; instead, follow manufacturer‑specific conversion tables as recommended by the NCCN [12][13].

Practical Conversion Algorithm (NCCN)

• Reduce by 25‑50 % if pain is well‑controlled [12][13].
• Use 100 % or increase by up to 25 % if pain is poorly controlled [12][13].
• For elderly or patients with renal/hepatic impairment, reduce by 50 % (as per the opening recommendation) [12][13].