Choice of opioid for pain in palliative care

Although morphineNational Institute for Health and Care Excellence (NICE), 2012. Updated 2016Wiffen, Wee, 2017 and oxycodoneSchmidt-Hansen, 2022 are the preferred opioids for pain management in palliative care, opioid choice depends on the general factors guiding analgesic choice listed in Factors influencing choice of analgesic in palliative care and the prescribing considerations in Choice of opioid in palliative care.

Transdermal opioid formulations (buprenorphine or, for patients stabilised on an oral opioid dose equivalent to oral morphine 30 mg per 24 hours or more, fentanyl) are useful for patients who:

• cannot swallow
• have impaired gastrointestinal absorption
• would have trouble adhering to the frequent administration of oral regimens
• prefer a nonoral option (eg for cultural or psychological reasons).

Although hydromorphone and methadone are used in palliative care, their prescription should be limited to healthcare professionals experienced in their use:

• Hydromorphone is easily confused with morphine but is approximately 5 times as potent. High-dose preparations of hydromorphone are available, further increasing the risk of serious harm if mistaken for morphine.
• Methadone has complex pharmacokinetic properties. It has a long and variable half-life; the potency and half-life of methadone differs between patients, causing variable interpatient analgesic effect. The time to reach steady-state concentration can be unpredictable and dose adjustment is extremely difficultSwarm, 2019.

The role of tapentadol for pain in palliative care is unclear; evidence to support its use is evolving, but dosing is limited by effects at other receptorsMercadante, 2017Swarm, 2019Wiffen, 2015.

Tramadol has a very limited role in pain management in palliative care because:

• data are inadequate to support its use; available data indicate it is unlikely to provide adequate analgesia for severe pain and is probably less effective than morphine for cancer painBandieri, 2016Fallon, 2018Tassinari, 2011Wiffen, Derry, 2017
• the maximum daily dose limits its practical use.

Codeine is not recommended for pain; it has no efficacy or tolerability advantage over an equianalgesic dose of morphine. Codeine is converted to morphine via cytochrome P450 2D6—rapid metabolisers may experience significant morphine-related adverse effects and poor metabolisers may have inadequate symptom relief.

For patients who already take codeine, tapentadol or tramadol, a change in opioid is not required unless the patient is experiencing (or is likely to experience) inadequate analgesia or adverse effects. See Switching opioids in palliative care for advice on calculating approximate equianalgesic doses.