Equianalgesic doses of opioids

In opioid-naive adults, equianalgesic opioid doses produce approximately the same analgesic effect. They are average equianalgesic doses calculated from pooled adult samples—exercise caution when using equianalgesic doses because significant pharmacokinetic and pharmacodynamic variations exist between individuals.

Equianalgesic doses are most commonly used when changing from one opioid to another, changing the route of administration, or when consolidating a opioid doses for a patient taking multiple opioids. If a patient is taking multiple opioids, calculate the oral morphine equivalent dose to quantify the total daily opioid intake.

Directly switching a patient from one opioid to another using a calculated equianalgesic dose can lead to overdose. An equianalgesic dose indicates the total daily dose, but not how to divide the dose over 24 hours. Consider the time to peak effect, and onset and offset of each opioid when changing opioid formulation or route of administration; see here for suggestions of how to change opioid formulation or route of administration.

Take into account the patient’s clinical condition (eg age, body mass, liver function, renal function, concomitant medications, mood and affect, and desired outcomes) and whether the patient is opioid tolerant. If the patient is unlikely to be opioid tolerant, the calculated equianalgesic dose may be appropriate. However, if the patient is opioid tolerant, halve the calculated equianalgesic dose and titrate to response.

Not all opioids are easily converted to an equianalgesic dose:

  • when changing from morphine to methadone, conversion factors vary considerably depending on the morphine dose. For this reason, methadone should only be prescribed by practitioners experienced in its use.
  • calculated equianalgesic doses of tapentadol or tramadol do not reflect equivalent opioid activity because there is reduced mu-receptor agonism and the analgesic effect is partly due to noradrenaline and/or serotonin reuptake inhibition. If changing from an opioid to tapentadol or tramadol, take an individualised approach and consider cross-tapering to avoid opioid withdrawal.

When calculating an equianalgesic dose in adults, use the calculator app available from the Faculty of Pain Medicine, see [URL]1; Approximate equianalgesic doses of opioids provides a summary of approximate equianalgesic opioid doses.

In children, seek specialist advice for calculating equianalgesic opioid doses.

Table 1. Approximate equianalgesic doses of opioids

Opioid [NB1]

Approximate equianalgesic doses

Oral

morphine (mg/day)

30 mg

codeine (mg/day) [NB2]

230 mg

hydromorphone (mg/day) [NB3]

6 mg

oxycodone (mg/day)

20 mg

tapentadol (mg/day) [NB4]

100 mg

tramadol (mg/day) [NB4]

150 mg

Parenteral [NB5]

buprenorphine (micrograms/day)

300 micrograms

fentanyl (micrograms/day)

150 micrograms

hydromorphone (mg/day)

2 mg

morphine (mg/day)

10 mg

oxycodone (mg/day)

10 mg

tramadol (mg/day)

100 mg

Sublingual

buprenorphine (micrograms/day)

750 micrograms

Transdermal [NB6]

buprenorphine (micrograms/hr)

15 micrograms per hour

fentanyl (micrograms/hr)

10 micrograms per hour

Note:

NB1: Equianalgesic doses of methadone are not included in this table because, when changing from methadone to morphine, conversion factors vary considerably depending on the morphine dose. For this reason, methadone should only be prescribed by practitioners experienced in its use.

NB2: Codeine has no role in pain management. Its inclusion in this table is to assist with changing a patient from codeine to an opioid that is suitable for pain management.

NB3: Prescription of hydromorphone should be limited to practitioners experienced in its use.

NB4: Doses of tapentadol or tramadol are not easily converted to equianalgesic opioid doses. Tapentadol and tramadol have reduced mu-receptor agonism compared to other opioids and the analgesic effect is partly due to noradrenaline and/or serotonin reuptake inhibition. If changing from an opioid to tapentadol or tramadol, take an individualised approach and consider cross-tapering to avoid opioid withdrawal.

NB5: Administration by different routes results in different times to peak concentration. When using the intravenous route, start with lower doses and titrate to effect.

NB6: Transdermal doses are expressed per hour, in line with available formulations.

Source: Faculty of Pain Medicine, Australian and New Zealand College of Anaesthetists (ANZCA). Opioid dose equivalence–Calculation of oral morphine equivalent daily dose (oMEDD). Melbourne: ANZCA; 2019. [URL]

1 If unable to use the opioid analgesic equivalence app, use the conversion factors published by the Faculty of Medicine to manually calculate an equianalgesic dose, see [URL].Return