Converting Methadone to Oral Morphine – NCCN Guideline Summary

Initial Conversion Ratio

The National Comprehensive Cancer Network (NCCN) recommends a 1:1 methadone‑to‑morphine conversion on day 1 when switching from methadone to morphine, to account for methadone’s long and variable half‑life and residual drug effect. 1

For a patient receiving 30 mg oral methadone daily, start with 30 mg oral morphine per day (e.g., 15 mg every 12 h as extended‑release). This conservative 1:1 ratio is used because a substantial amount of methadone remains in the body on the first day of conversion. 2

Dose adjustments should be made every 1–2 days as methadone clears, because the conversion ratio changes during the clearance phase. 1
Standard equianalgesic tables should not be used for conversions from methadone, as they underestimate methadone’s potency in chronic use. 2
Total daily morphine consumption (regular + breakthrough) must be monitored to guide dose titration. 3
The extended‑release morphine dose should be adjusted daily based on the amount of breakthrough medication required. 3
Morphine requirements typically increase over the first 3–7 days as residual methadone effects diminish. 1

Provide immediate‑release morphine equal to ~10 % of the total daily morphine dose (approximately 5–10 mg) every 2–4 hours as needed for breakthrough pain during the conversion period. 2

Do not abruptly discontinue methadone without adequate morphine coverage, to avoid withdrawal and uncontrolled pain. 3
Methadone clearance takes 1–2 days for substantial reduction and several days for complete elimination, necessitating ongoing dose reassessment beyond the first 24 hours. 3
Avoid rigid reliance on conversion tables when converting from methadone, because individual variability is substantial. 1
Closely monitor for signs of inadequate analgesia or opioid withdrawal throughout the first week of conversion. 3

The most dangerous error is using the morphine‑to‑methadone conversion ratio (4:1–12:1) in reverse; those ratios apply only when converting to methadone, not from methadone. 4
Applying a 1:8 ratio on day 1 would severely underdose (e.g., 3.75 mg morphine for 30 mg methadone), leading to withdrawal. 1
The 1:1 ratio is recommended only for day 1; subsequent dose increases should be guided by clinical response and patient‑specific factors. 2