What are the diffrent drugs used in each step of the WHO pain ladder?
Step 1 (non-opioid analgesia):
Step 2 (weak opioids):
Step 3 (strong opioids):
How are doses of weak opioids (e.g. codeine) converted to oral morphine?
24hr dose of oral morphine = 24hr dose of codeine ÷ 10
What are the different formulations of oral morphine and how are the two converted between?
- Morphine sulfate immediate release (Oromorph) effect lasts for 4hrs
- Morphine sulfate modified release (MST) effect lasts for 12hrs
- In patients who have been just taking oromorph, total dose over 24hrs is divided by 2 to determine the dose of MST needed to be given per dose BD (e.g. if patient takes 40mg oromorph over 24hrs, they should be given 20mg MST BD to gain the same effect)
How is dosage of oral morphine determined for breakthrough pain?
Breakthrough pain = Dose in 24hrs ÷ 6
What is the stepwise approach to initiating strong opioids from weak opioids or from scratch?
- The 24hr dose of oromorph should be calculated either from the 24hr dose of weak opioids, or 15mg/24hrs if starting from scratch
- This should then be divided by 6 to determine the dose that should be given 4-hourly, with same doses given PRN if pain control insufficient
- Once total 24hr dose of morphine needed for pain control is determined, switch to BD administration of MST morphine
How are doses of oral morphine converted to subcutaneous morphine or diamorphine
- 24hr dose of morphine SC = 24hr dose of morphine PO ÷ 2
- 24hr dose of diamorphine SC = 24hr dose of morphine PO ÷ 3
How is dosage of morphine SC and diamorphine determined for breakthrough pain?
Divide 24hr doses by 6
What are the prominent side-effects of morphine?
- Vivid dreams
- Visual hallucinations
- Cognitive slowing
- Myotonic jerks
- Respiratory depression
What laxatives need to be prescribed with morphine?
Stimulant laxative (e.g. senna, bisacodyl) + stool softener (e.g. docusate, glycerol)
What anti-emetic needs to be prescribed with morphine?
Haloperidol for morphine-induced nausea & vomiting
What are the drugs used to treat neuropathic pain?
How should intestinal colic be treated?
Hyoscine butylbromide (anti-spasmodic)
How should bone pain be managed?
- Standard analgesia
- Palliative radiotherapy
- Bisphosphonates may be effective against lytic bone lesions, but not sclerotic lesions
How are doses of oral morphine converted to oxycodone?
24hr dose of oral oxycodone = 24hr dose of oral morphine ÷ 1.5
What are the different formulations of oxycodone?
- Oxynorm (short-acting) effect lasts for 4hrs
- Oxycontin (long-acting) effect lasts for 12hrs
How are doses of oral oxycodone converted to subcutaneous oxycodone?
24hr dose of S/C oxycodone = 24hr dose of oral oxycodone ÷ 1.5
How are doses of oral morphine converted to alfentanyl?
24hr dose of alfentanyl = 24hr dose of oral morphine ÷ 30 or 24hr dose of diamorphine ÷ 10
Which analgesics are safe to use in patients with renal failure and which are not?
- Avoid codeine
- Tramadol can be used with caution
- Avoid morphine, diamorphine and oxycodone
- Fentanyl or alfentanyl can be used
Summary of strong opioid conversions