The opioid doses shown in the table below are therapeutically equivalent doses.
All doses are in milligrams, except Fentanyl which is listed in micrograms.

These data are presented to allow conversion between different opioids and different administration routes.
Further notes regarding dose equivalence are presented below the table.
Please refer to individual monographs for specific drug information.

Opioid dose equivalence
Fentanyl patch:
(use with caution in opioid naive patients; takes 8-12 hours for effect with residual effect for 14-24 hours after patch removed)

25 mcg patch equivalent to:
- Morphine 50mg po over 24 hour period
- Morphine 16mg i/v over 24 hour period

50 mcg patch equivalent to:
- Morphine 100mg po over 24 hour period
- Morphine 32mg i/v over 24 hour period

Morphine/Methadone conversion ratios:
The ratio changes as the morphine dose increases
Calculate equianalgesic dose then reduce by 25-50%

Ratio of 24-hour oral morphine: oral methadone
For <90 mg of morphine = 4:1
For 91-300 mg of morphine = 8:1
For 301-600 mg of morphine = 12:1

Oral methadone:IV/IM methadone = 2:1
Seek expert Pain Team or Palliative Care advice if unsure or complex patient
References:
CCDHB Pain Management Guidelines by Dr.Paul Glover, Dept. of Anaesthesia (2009)