Robertson et al^{149} |
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Conversion of continuous intravenous fentanyl of 7–14 d duration to enteral methadone: |

1. By using the current hourly infusion rate, calculate the 24-h fentanyl dose. |

2. Multiply the daily fentanyl dose by a factor of 100 to calculate the equipotent amount of methadone (ratio of potencies assumed to be fentanyl: methadone = 100:1). |

3. Divide this amount of methadone by 6 (a correction for the longer half-life of methadone) to calculate an initial total daily dose of methadone, and on day 1 provide this amount orally in 4 divided doses every 6 h for 24 h. |

4. Day 2: Provide 80% of original daily dose in 3 divided oral doses every 8 h for 24 h. |

5. Day 3: Provide 60% of original daily dose in 3 divided oral doses every 8 h for 24 h. |

6. Day 4: Provide 40% of original daily dose in 2 divided oral doses every 12 h for 24 h. |

7. Day 5: Provide 20% of original daily dose × 1. |

8. Day 6: Discontinue methadone. |

Conversion of continuous intravenous fentanyl greater than 14 d duration to enteral methadone: |

1. Repeat steps 1–2 above. |

2. Days 1–2: Divide the dose of methadone by 6 (a correction for the longer half-life of methadone) and on day 1 provide this amount orally in 4 divided doses every 6 h for 48 h. |

3. Days 3–4: Provide 80% of original daily dose in 3 divided oral doses every 8 h for 48 h. |

4. Days 5–6: Provide 60% of original daily dose in 3 divided oral doses every 8 h for 48 h. |

5. Days 7–8: Provide 40% of original daily dose in 2 divided oral doses every 12 h for 48 h. |

6. Days 9–10: Provide 20% of original daily dose once per day for 48 h. |

7. Day 11: Discontinue methadone. |

For patients on continuous intravenous morphine, proceed as above but do not multiply the daily fentanyl dose by 100, because morphine and methadone are nearly equipotent. |

Meyer and Berens^{150} |
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Conversion of continuous intravenous fentanyl to intermittent intravenous morphine: |

1. By using the target hourly infusion rate of fentanyl, calculate the 24-h fentanyl dose. |

2. Multiply the daily fentanyl dose by a factor of 60 to calculate the equipotent dose of morphine (ratio of potencies assumed to be fentanyl: morphine = 60:1). |

3. Divide the dose of morphine by 4 (correcting for the longer half-life of morphine) and on day 1 administer this amount intravenously in 6 divided doses every 4 h. |

4. Titrate the morphine dose for adequate effect over 12 to 24 h. |

Conversion of intermittent intravenous morphine to enteral methadone: |

1. Multiply the dose of morphine given every 4 h by 2 (ratio of potencies assumed to be morphine: methadone = 2:1) to determine an equipotent amount of methadone. |

2. Provide this amount of methadone as an oral dose every 12 h for 3 doses. |

3. Double this amount of methadone and provide as a single oral dose per day at bedtime. |

4. Provide 90% of the initial dose on day 2, 80% on day 3, etc, so that the last dose of methadone (10% of the original dose) is given on day 10. |

Protocols at Wolfson Children’s Hospital, Jacksonville, Florida |
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Conversion of continuous intravenous fentanyl >7 d duration to enteral methadone: |

1. By using the current hourly infusion rate, calculate the 24-h fentanyl dose. |

2. Multiply the daily fentanyl dose by a factor of 100 to calculate the equipotent amount of methadone (ratio of potencies assumed to be fentanyl: methadone = 100:1). |

3. Divide this amount of methadone by 8–12 (a correction for the longer half-life of methadone) to calculate an initial total daily dose of methadone (not to exceed 40 mg/day). |

4. Days 1–2: Provide the total daily dose of methadone orally in 4 divided doses every 6 h for 48 h. At the time of the second methadone dose, reduce the fentanyl infusion rate to 50%; at the time of the third dose, reduce the fentanyl infusion rate to 25%; and after the fourth methadone dose, discontinue the fentanyl infusion. |

5. Days 3–4: Provide 80% of original daily dose in 3 divided oral doses every 8 h for 48 h. |

6. Days 5–6: Provide 60% of original daily dose in 3 divided oral doses every 8 h for 48 h. |

7. Days 7–8: Provide 40% of original daily dose in 2 divided oral doses every 12 h for 48 h. |

8. Days 9–10: Provide 20% of original daily dose once per day for 48 h. |

9. Day 11: Discontinue methadone. |

Conversion of continuous intravenous midazolam >7 d duration to enteral lorazepam: |

1. By using the current hourly infusion rate, calculate the 24-h midazolam dose. |

2. Because lorazepam is twice as potent as midazolam and has a sixfold longer half-life, divide the 24 h midazolam dose by 12 to determine the daily lorazepam dose. |

3. Divide the calculated lorazepam dose by 4 and initiate every 6 h oral treatments with the intravenous product or an aliquot of a crushed tablet. |

4. Wean lorazepam by 10% to 20% per day. The dosage interval can also be increased gradually to every 8 h, then every 12 h, then every 24 h, and then every other day before lorazepam is discontinued. |

Summary of Conversion Of Intravenous Opioids to Enteral Methadone |

1. Tobias et al^{147}: Converted 2 patients on morphine (0.1–0.15 mg/kg q3h) and 1 patient on fentanyl (1–2 µg/kg every 1–2 h) to methadone at a starting dose of 0.2 mg/kg per day. |

2. Robertson et al^{149}: 1 µg/kg per h fentanyl = 0.4 mg/kg per day methadone. |

3. Meyer and Berens^{150}: 1 µg/kg per h fentanyl = 0.24 mg/kg per day methadone. |

4. Wolfson Children’s Hospital: 1 µg/kg per h fentanyl = 0.2–0.3 mg/kg per day methadone. |