Choosing an Opioid
To see more information about each opioid, please select from the following:
There is no evidence that any one opioid is significantly more efficacious or less toxic than any other at an equianalgesic dose. The choice of opioid depends on a number of factors:
Ability to swallow:
oral route is preferred; if unable to swallow or compromised GI tract consider transdermal route (e.g. fentanyl patch, buprenorphine patch) or parenteral route (most commonly subcutaneous).
Impaired renal function:
avoid morphine (can be used at lower doses, less frequently), caution with oxycodone or hydromorphone. Recommended opioids are fentanyl, buprenorphine or methadone.
Impaired liver function:
caution with oxycodone/naloxone controlled release preparations
Allergies/intolerance:
rare, often reflects previous adverse event (e.g. nausea and vomiting following post-op opioids). If true allergy, rotate to opioid of different class (see classification).
Constipation/ileus/bowel obstruction:
slowing of bowel transit time is a common feature of all opioids. Lipophilic opioids (fentanyl, buprenorphine) may be less constipating. Consider combination preparation of oxycodone and naloxone (Targin®), or parenteral formulations.
Age:
morphine may be less well tolerated in the elderly (probably as a reflection of impaired renal function). Buprenorphine patches (Norspan®) give a continuous infusion of low-dose opioid.
Cognitive function:
consider once daily formulations or tablets/capsules that can be delivered in Webster packs where cognitive function is impaired.
Compliance:
consider transdermal preparations for improved compliance.
Cost:
not all opioids are subsidised by the PBS.
Availability:
some countries impose strict limitations on availability of opioids.
Experience:
use a limited number of opioids and become familiar with their use; patients with difficult pain should be referred to palliative care or pain specialists.