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

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

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

Buprenorphinesublingual

- 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

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