approximate relative potencies of opioids (opiates) in chronic usage in comparison to morphine
These conversions are a guide only (1,2,3,4) - 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
- the NHS Specialist Pharmacy Service (SPS) have published updated advice for prescribers switching between morphine and alternative opioids, using a stepped process. Full details can be found on SPS website at Switching between oral morphine and other oral opioids in adult palliative cancer care patients
|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)|
PR (rectal route) 1
- see manufacturer's SPC
|60||0.2 mg = 200 micrograms||-||6-8|
|Dextropropoxyphene (1) **||1/10||100mg||-||4-6|
|Fentanyl||see linked item below|
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)
- (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