The opioid trial

If the prescriber and patient agree that opioid therapy may play a role in further management of the patient’s pain, a trial of opioid therapy should be planned. The opioid trial establishes whether the patient achieves any reduction in pain with use of opioids. It is important to remember that short term response to opioid therapy does not predict long term therapy which may be limited by adverse effects or declining efficacy. Achieving optimal doses and managing side effects of opioids is not the purpose of the trial; these can be explored once it has been shown whether opioids are helpful for the patient.

Starting the trial

The patient and prescriber should agree some readily assessable outcomes that indicate that opioids may play a role in the patient’s management. These will usually include reduction in pain intensity and ability to achieve specific functional improvement facilitated by the medication. For patients in whom sleep is significantly impaired by pain, improved sleep would be a reasonable outcome. 

Duration of the opioid trial

This will depend on the periodicity of the patient’s pain. If the patient has constant pain, the opioid trial may be concluded in one or two weeks. If the patient has intermittent disabling flare ups of pain on a background of more manageable symptoms, the trial should be long enough to observe the effect of opioids on two or three episodes of increased pain.

Choice of opioid formulation and dose

Where possible, the usefulness of opioids should be explored by prescribing a short (1-2 week supply) of immediate release morphine tablets or liquid. The patient may be advised to explore different doses within a specified range eg, morphine 5-10mg. If reduction in pain is not achieved following a single dose of immediate relief morphine 20mg, opioids are unlikely to be beneficial in the long term. A trial of fixed dose regimens using modified release preparations needs to allow for one or two upwards dose adjustments and may therefore take three weeks or more. 

Assessing whether the opioid trial is a success

The patient should keep a diary during the opioid trial. This should include a twice-daily report of pain intensity, comment on sleep, note of activity levels and how any of these are changed following a dose of opioid. All doses of opioid should be recorded in the diary with a comment on side effects. If the opioid trial is not successful, the drugs should be tapered and stopped within one week.

If the patient reports no improvement in symptoms following the trial it is very unlikely that long-term opioid therapy will be helpful.


All stages of the opioid trial should be clearly documented and if appropriate, a copy of the agreed aims of therapy and how these may be monitored should be given to the patient. Documentation should also include the agreed starting dose and formulation of drug and details of planned dose escalation. If the opioid trial demonstrates that the medicines are unhelpful, the reasons for this (lack of efficacy/intolerable adverse effects) should also be clearly documented. If the patient reports reduction in pain but at the cost of side effects that preclude achievement of functional goals, it is reasonable to explore different dosing regimens with active management of side effects to see if a useful balance between benefits and harms can be achieved.


If the opioid trial demonstrates some benefit from opioids, further exploration of opioid treatment may be helpful. A successful short-term opioid trial does not predict long-term efficacy. Click here for guidance on long-term prescribing of opioids.