Considerations when using opioids for acute pain in patients who take regular opioid therapy in palliative care

Patients who take regular opioid therapy in palliative care need careful consideration when managing acute pain.

If an opioid is indicated for the management of acute pain in a patient with palliative care needs who takes regular opioid therapy, give the as-required opioid dose that has been prescribed for breakthrough pain. If the patient has not been prescribed an as-required opioid dose for breakthrough pain, see Immediate-release opioid therapy for breakthrough pain in patients who take regular opioid therapy for advice on calculating the dose. Example of calculating an intravenous dose of morphine for severe, acute nociceptive pain in a patient taking modified-release oxycodone shows an example of a dose calculation for a patient with severe, acute nociceptive pain who takes a regular opioid but does not have a breakthrough opioid prescribed.

If parenteral administration of an opioid is required for acute pain, convert the dose prescribed for breakthrough pain to a parenteral equianalgesic opioid dose—see Approximate equianalgesic doses of opioids in palliative care for approximately equianalgesic doses of opioids.

Patients who take regular opioid therapy may, on some occasions, need slightly higher doses than the calculated breakthrough opioid dose—seek expert advice early if initial management of acute pain is not effective.

Additional opioid doses should be titrated according to the impact of the pain on functional activity, the sedation score, presence of adverse effects (eg opioid-induced ventilatory impairment), and pharmacokinetics of the opioids being used.

For additional considerations in managing acute pain in patients who are opioid tolerant, see Managing acute pain in opioid-tolerant patients in the Pain and Analgesia guidelines.

Table 1. Example of calculating an intravenous dose of morphine for severe, acute nociceptive pain in a patient taking modified-release oxycodone

Original dose

A patient taking oxycodone modified-release 60 mg orally, twice daily has severe, acute nociceptive pain requiring conversion of their oral oxycodone to intravenous morphine.

Calculation [NB1]

oral oxycodone 60 mg twice daily is oral oxycodone 120 mg in 24 hours

oral oxycodone 120 mg in 24 hours is equivalent to oral morphine 180 mg in 24 hours [NB2]

oral morphine 180 mg in 24 hours is equivalent to intravenous morphine 60 mg in 24 hours [NB2]

Initial intravenous morphine dose

Use one-twelfth to one-sixth of the 24-hour intravenous morphine dose: morphine 5 to 10 mg intravenously

Note:

NB1: Confirm manual calculations using a digital opioid conversion calculator (eg eviQ calculator or the Australian and New Zealand College of Anaesthetists (ANZCA) Faculty of Pain Medicine opioid calculator and application), or check them with a palliative care specialist, pharmacist or colleague. Seek expert advice when switching opioids in patients taking more than 100 mg oral morphine (or equivalent) in 24 hours.

NB2: See Approximate equianalgesic doses of opioids in palliative care for approximate equianalgesic opioid doses. For acute severe pain, direct equianalgesic doses of opioids are used when switching opioids rather than the usual suggested 50 to 75% of the calculated dose equivalent.