Opioid Analgesics: Approximate Potency Equivalence with Oral Morphine

Guide to potencies of opioid analgesics, for dose conversion.

Approximate Potency Equivalence with Oral Morphine
ORAL
ANALGESICCONVERSION RATIO TO ORAL MORPHINERECOMMENDED DOSING FREQUENCYAVAILABLE FORMULATIONS
Codeine 0.1 4-hourly Tabs, oral soln
Dihydrocodeine 0.1 4–6-hourly (or 12-hourly if SR tabs) Tabs, SR tabs, oral soln
Hydromorphone 5–7.5 4-hourly (or 12-hourly if SR caps) Caps, SR caps
Methadone Variable 6–8-hourly Tabs
Morphine 1 4-hourly (or 12-hourly if SR prep) Tabs, SR tabs, SR caps, oral soln, granules for susp
Oxycodone 1.5–2 4–6-hourly (or 12-hourly or once daily for SR tabs) SR tabs, caps, oral soln
Pethidine* 0.1 4-hourly Tabs
Tramadol 0.1 4–6-hourly (or 12-hourly or once daily for SR preps) SR tabs, caps, SR caps, oral soln, orodispersible tabs, sol tabs
SUBLINGUAL
ANALGESICCONVERSION RATIO TO ORAL MORPHINERECOMMENDED DOSING FREQUENCYAVAILABLE FORMULATIONS
Buprenorphine 80 6–8-hourly or prn Sublingual tabs
SUBCUTANEOUS
ANALGESICCONVERSION RATIO TO ORAL MORPHINERECOMMENDED DOSING FREQUENCYAVAILABLE FORMULATIONS
Diamorphine 3 4-hourly Inj
Methadone Variable 6–8-hourly Inj
Morphine 2 4-hourly Inj
Oxycodone 2 4-hourly Inj
INTRAMUSCULAR
ANALGESICCONVERSION RATIO TO ORAL MORPHINERECOMMENDED DOSING FREQUENCYAVAILABLE FORMULATIONS
Morphine 2 4-hourly Inj
TRANSDERMAL
Refer to separate table Initiating Treatment with Transdermal Opioids

Multiply by the potency ratio to convert an opioid dose to the equivalent dose of oral morphine
e.g. oral dihydrocodeine 30mg qds = 120mg/day; 120mg x 0.1 = 12mg oral morphine/day

Divide by the potency ratio to convert an oral morphine dose to the equivalent dose of another opioid
e.g. oral morphine 30mg bd = 60mg/day; 60mg/2 = 30mg subcutaneous oxycodone/day

  • The conversion ratios in the above table are approximate and are included to provide guidance only.
  • Doses will need to be titrated up or down for individual patients.
  • When converting at high doses (eg, morphine or equivalent doses of ≥1g/24 hrs) it is recommended to use a lower than calculated dose (eg, ≥50% lower) – prn doses may be used to make up any deficit while titrating to a satisfactory dose of the new opioid.
  • These ratios may differ from local formularies or guidance.

    Approximate relative potencies taken from Twycross R, Wilcock A, Howard P. Palliative Care Formulary (5th ed). Nottingham: Palliativedrugs.com Lyd, 2014. www.palliativedrugs.com

    *Use of pethidine in palliative care is discouraged.


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