Reasons for switching
NICE Clinical Guideline 140: Palliative care for adults: strong opioids for pain relief recommends morphine as the first-line strong opioid for maintenance treatment of pain in palliative care patients with advanced and progressive cancer, so prescribers may wish to switch from other opioids to morphine.
In some cases, however, other opioids may be preferred to morphine. For example, if a patient isn’t getting sufficient pain relief with morphine or is suffering from, or is at risk of, side effects.
Scope of our advice
Our advice only applies to opioids prescribed for oral administration in adults for pain management in palliative cancer care settings. We cover dosing equivalences only, rather than choice of opioid.
If your opioid conversion is outside this scope, you should consult national or local guidelines, or seek advice from a relevant specialist service, or contact your regional medicines information centre.
Other information sources
In addition to our tool, healthcare professionals may come across several information sources (e.g. websites, journal articles, reference books etc) offering guidance on opioid dose equivalences. Make sure the information sources you use are reliable and applicable to your clinical scenario.
You may need to look in a few places to find information on dose equivalences before making a clinical judgement on what dose to prescribe for an individual patient.
You should bear in mind that dose equivalences are always an approximate guide only, because we don’t have a great deal of precise data.
Information sources may differ in the equivalent doses they quote and there will also be variation between individuals.
Apply a stepped process when switching
Applying the stepped process outlined below will support you in making a safe switch for your patient.
A NICE Clinical Knowledge Summary on Palliative Cancer Care – pain advises primary care healthcare professionals to “Seek specialist advice or consult local guidelines (where available) when selecting the opioid and dose to switch to. This is because experience in primary care is likely to be limited and alternative oral opioids are best initiated by a person with experience in palliative care.”
It is important to consider other strategies if people are suffering from, or are at risk of, side effects, such as:
- non-pharmacological pain relief
- reducing the opioid dose (and possibly adding adjuvant analgesics)
- symptomatic management of the side effect, or
- switching the route of administration.
You may also find information on switching opioids and dose equivalences in specialist palliative care reference sources, such as The Palliative Care Formulary (subscription required), or in national or local palliative care guidelines, such as the Scottish Palliative Care Guidelines: Choosing and Changing Opioids
For official manufacturer’s information, the best place to look would be the Summary of Product Characteristics (SmPC) for the opioid analgesic the patient will be switching from or to, not the morphine SmPC. SmPCs for most opioid analgesics provide information on dose equivalences or potency to morphine. The SmPC may also provide specific advice on prescribing for patients who have been taking morphine or other opioid analgesics.
You can find SmPCs for most medicines on the eMC or MHRA websites. The information on dose equivalences or switching will usually be in section ‘4.2 Posology and Method of Administration’ or ‘5.1 Pharmacodynamic effects’.
Follow further steps below.
The total daily dose of the current opioid(s), including all long-acting and breakthrough doses, must be determined prior to conversion. If the patient is on multiple opioids, convert all to morphine equivalents.
Use our tool to identify the approximate potency equivalence, and follow the directions given in the tool to calculate an equivalent morphine or non-morphine opioid dose.
The usual starting point is to reduce the calculated dose of the new opioid by 25 to 50%.
But you will need to consider individual patient factors to decide whether or not to apply a dose reduction.
High risk patients
A dose reduction is particularly important when:
- using high doses
- people are at increased risk from opioids (e.g. older, frail patients or those with co-existing medical conditions)
- people have not tolerated or have had side effects with the opioid they are switching from
- there has been a rapid dose escalation of the opioid being switched
In these cases a dose reduction of at least 50% would be recommended.
Low risk patients
Dose reduction may not be necessary in younger patients with no other medical conditions or for patients taking low doses.
Patients with severe pain
In cases where the original opioid has failed to control pain or if the individual is experiencing severe pain, it may be better not to reduce the dose and to prescribe the calculated equivalent dose.
Consider the following:
- Ask a colleague to double-check your calculations.
- Seek specialist advice
- Seek advice from your regional medicines information centre
Patients on a regular strong opioid should also have an opioid prescribed ‘as required’ (‘prn’) for breakthrough pain. These should not be modified-release preparations.
Scottish Palliative Care guidelines suggest an appropriate ‘prn’ dose is typically one-sixth to one-tenth of the regular opioid dose.
A NICE Clinical Knowledge Summary on palliative cancer care – pain provides advice on titrating oral morphine doses.
NICE guidelines advise that patients will need frequent review, particularly in the titration phase, to make sure their pain is adequately controlled and they do not suffer serious side effects. Specialist advice may be needed if, after a few dose adjustments, a good balance between pain control and side effects is not reached.
Make sure patients and family or carers are advised of the signs and symptoms of opioid overdose (drowsiness, shallow breathing, pinpoint pupils) and know they need to seek immediate medical help if they occur.
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- Added bibliography
- Following internal QA check: text amended to better reflect wording in NICE guideline re: morphine being opioid of choice