approximate relative potencies of opioids (opiates) in chronic usage in comparison to morphine

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These conversions are a guide only (1,2,3,4) - seek expert advice and consult local guidelines

Analgesic Potency ratio to oral morphine approximate equivalence to 10mg oral morphine on repeat dosing for oral dose approximate equivalence to 10mg oral morphine on repeated dosing for subcutaneous dose/IM dose Duration of action (hours)
Morphine

1

PR (rectal route) 1

10mg 5mg 3-6

Buprenorphine sublingual

- see manufacturer's SPC

60 0.2 mg = 200 micrograms - 6-8
codeine* 1/10 100mg - 3-5
Diamorphine 1 10mg 3mg 3-4
Dihydrocodeine 1/10 100mg - 4-6
Dextropropoxyphene (1) ** 1/10 100mg - 4-6
Tramadol (3) 1/10 100mg - 4-5
Fentanyl see linked item below      
phenazocine (1) 5 2mg - 6-8
Alfentanil    

0.3mg = 300 micrograms

Seek specialist palliative care advice

 

30 minutes IM

60 minutes SC

Hydromorphone   1.3mg 0.6 mg = 600 microgram 3-4 hours
Oxycodone   5mg*** 2.5 4 -6 hours

* determined for parenteral but also appears to apply to oral route

** methadone and dextropropoxyphene have prolonged half lives leading to accumulation when given repeatedly (1)

*** manufacturers guidelines of 2:1 ratio of oxycodone : morphine (note other conversions use a 1.5:1 ratio for oxycodone : morphine) (3)

NHS tool to calculate estimated dose equivalences of oral morphine to other oral opioids (4)

Reference:

  • (1) West Midlands Palliative Care Physicians (2003). Palliative care - guidelines for the use of drugs in symptom control.
  • (2) West Midlands Palliative Care Physicians (2007). Palliative care - guidelines for the use of drugs in symptom control.
  • (3) West Midlands Palliative Care Physicians (2012). Palliative care - guidelines for the use of drugs in symptom control.
  • (4) NHS Specialist Pharmacy Service (October 2021). Switching between oral morphine and other oral opioids in adult palliative cancer care patients

Last edited 12/2021 and last reviewed 12/2021

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