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

These conversions are a guide only - seek expert advice and consult local guidelines

at high doses, conversion from one opiate to another must always be reviewed cautiously to avoid sudden opiate toxicity.Take particular care if converting high doses of oral opiates to subcutaneous (s.c.) infusions

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)

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.

Last reviewed 11/2019

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