This advice is sourced from Dr Ros Taylor a senior palliative physician
Q. How do I decide when it is appropriate to start a patient on a strong opioid and what is best practice?
The WHO ladder recommends regular analgesia by mouth for severe cancer pain. The steps are:
- Non-opioids (e.g. Paracetamol and NSAIDs)
- Weak opioids (e.g. Codeine and Tramadol) Both are a tenth as strong as Morphine i.e. 60mg Codeine = 6mg Morphine, 240mg Codeine = 24mg Morphine.
- Strong opioids (e.g. Morphine, Fentanyl, Oxycodone, Methadone, Buprenorphine) until the patient is free of pain
At each step adjuvants should be considered e.g. medicines for neuropathic pain, bone pain, or pain caused by spasm, rather than simply escalating the opioid.
Some pains are not opioid sensitive - increasing the dose may lead to toxicity rather than improved pain control.
Stepping up from a weak to a strong opioid (step 2 to 3 above)
If a full dose of a weak opioid (e.g. Co-codamol 500/30 - 8 daily - step 2) is not giving 24 hour pain relief, then consider stepping up to a strong opioid.
The gold standard is Morphine oral solution (10mgs/5 mls) used regularly e.g. 2mg - 5mg mgs 4 hourly and titrate as needed.
Once a steady dose is reached then convert to 12 hourly modified release e.g. MST or Zomorph. E.g. if a patient is needing 5mgs six times a day (30mgs total daily dose), then can convert to Morphine Modified Release Tablets 15mgs twice daily.
A PRN dose will be needed to manage breakthrough pain - prescribe 1/6 of the 24 hour Morphine dose. The right PRN dose should last at least 3 hours.
Renal Failure
As renal function worsens it is safer to use low doses of short-acting liquid options such as low dose Oxycodone, which evidence suggests may be slightly safer than Morphine in advanced renal failure (eGFR<30)
Fentanyl patches
Fentanyl patches are also a good option if patients are not safely swallowing, poorly compliant with oral medications, very constipated or are vomiting. (There is evidence that Fentanyl is less constipating than Morphine or oral Oxycodone)
Fentanyl patches are changed every 72 hours and the lowest dose is 12mcg per hour which is equivalent to approximately 30mg - 40mg of Morphine per 24 hours.
Remember to prescribe a laxative and possibly an antiemetic. Laxatives will need to continue but antiemetics may only be needed when starting opioids or increasing the dose.
It is always good to explore a patient's concerns and beliefs when starting a medicine such as Morphine.